Introduction to the world of nunclear physics. Methododical manual on the translation of scientific and technical texts 9786010400863, 9786012479904, 9786010400153, 9786010400115

Citation preview

KAZAKH NATIONAL UNIVERSITY AFTER AL-FARABI

INTRODUCTION TO THE WORLD OF NUCLEAR PHYSICS Methodological manual on the translation of scientific and technical texts

Author-compiler: L.E. Strautman, Sh.B. Gumarova, V.Zh. Sarsekenova

Almaty «Kazakh university» 2013

UDC 811.111 BBK 81.2Angl. I 665 Recommended for the Academic Council of the Faculty of Philology, Literary Studies and World Languages and RISO KazNU after al-Farabi

Reviewers: Doctor of physical and mathematical sciences, professor N.T. Burtebayev Doctor of pedagogical sciences, professor R.A. Shakhanova Candidate of physical sciences, docent I.A. Baymuratova

I 665

Introduction to the World of Nuclear Physics: methodological manual on the translation of scientific and technical texts / author-compiler: L.E. Strautman, Sh.B. Gumarova, V.Zh. Sarsekenova.  Almaty: Kazakh university, 2013. – 10 p. ISBN The main purpose of the textbook is to provide students of the Pre-Intermediate and Intermediate levels with educational material on specialty “”Nuclear Physics” in English. This textbook is designated for practical work with the 1-2-year students of specialty “Nuclear Physics” at physico-technical faculty, it can also be used as an additional material for individual work of students of physico-technical faculty.      –    Pre-Intermediate  Intermediate       « »    .        1-2  -      « »,  ! !                 -  .

UDC 811.111 BBK 81.2Angl. © Strautman L.E., Gumarova SH.B., Sarsekenova V.Zh., 2013 © KazNU after al-Farabi, 2013 ISBN

      –    Pre-Intermediate  Intermediate      ,          . "          . "  #   $ , %#  %   () , %     Headway, English Files   Cutting Edge. &            ? '   ,   *  ,     +  . " %   #     (General English)  $        ,  +         . /,   %  ,     ! must, have to, should ought to. 4  +   ,   must  have to,     . "    !   +       . 9     $         %  $  ,       must, have to, should ought to. ;    !  :        have to,   %#  $       must.   % -      3

   !         + ,   %  !  [1]. /  ,   ,         !      . +   !  ,         . "     % %   ,      #    !  .       ! – +   ! [3].  !  ,     ,  !   ,  %#  , +  +           . /          ,   $    !  !         .      %    ,   $  ,      #    . +   !         ,           .

UNIT I Vocabulary list particle 1)  ;   )  $  ,  - . )  $    - . alpha particle –  -  elementary particle – +    subatomic particle –    particle detector  

electric charge +    strength 1)  2)  3)    4)   5)  6) # strength properties   field strength  !  force field     shell 1)   2) $ $ 3) $ $ 4)   5)  6)  # 7)  8)   9)   valence   ,   valence band electron – +     compound 1) , ,   ;  Proteins are by far the most complex chemical compounds. – ; ,   ,  %   !   . Syn: mixture, blend, union, combination 2)  ,   !  chemical compound   combination 1)   2)   3)  4) * 5)  6)   7) # 8)  9)  10) # combination of n things r at a time –   n +   r 5

ELECTRIC CHARGE

Electrons Electrons are the smallest and lightest of the particles in an atom. Electrons are in constant motion as they circle around the nucleus of that atom. Electrons are said to have a negative charge, which means that they seem to be surrounded by a kind of invisible force field. This is called an electrostatic field. Protons Protons are much larger and heavier than electrons. Protons have a positive electrical charge. This positively charged electrostatic field is exactly the same strength as the electrostatic field in an electron, but it is opposite in polarity. Notice the negative electron and the positive proton have the same number of force field lines in each of the diagrams. In other words, the proton is exactly as positive as the electron is negative. Like charges repel, unlike charges attract Two electrons will tend to repel each other because both have a negative electrical charge. Two protons will also tend to repel each other because they both have a positive charge. On the other hand, electrons and protons will be attracted to each other because of their unlike charges. Since the electron is much smaller and lighter than a proton, when they are attracted to each other due to their unlike charges, the electron usually does most of the moving. This is because the protons have more mass and are harder to get moving. Although electrons are very small, their negative electrical charges are still quite strong. Remember, the negative charge of an electron is the same as the positive electrical charge of the much larger in size proton. This way the atom stays electrically balanced. Another important fact about the electrical charges of protons and electrons is that the farther away they are from each other, the less force their electric fields have on each other. Similarly, the closer they are to each other, the more force they will experience from each other due to this invisible force field called an electric field. 6

THE FREE ELECTRON Maintaining electrical balance Each basic element has a certain number of electrons and protons, which distinguishes each element from all other basic elements. In most elements, the number of electrons is equal to the number of protons. This maintains an electrical balance in the structure of atoms since protons and electrons have equal, but opposite electrostatic fields. Pictured here is an atom of copper, which is much more complex than either an atom of hydrogen or helium. The copper atom has 29 protons in its nucleus with 29 electrons orbiting the nucleus. Notice that in the copper atom, the electrons are arranged in several layers called shells. This is to graphically represent that the electrons are at different energy levels within the atom. The energy of an electron is restricted to a few particular energy levels. The energy is said to be quantized, meaning that it cannot vary continuously over a range, but instead is limited to certain values. These energy levels or shells follow a very predictable pattern. The closest shell to the nucleus can have up to 2 electrons. The second shell from the nucleus can have up to 8 electrons. The third shell can have up to 18 electrons. The fourth shell can have up to 32 electrons, and so on. Atoms can have this many electrons, but they do not have to have this many electrons in each shell. The greater distance between the electrons in the outer shells and the protons in the nucleus means the outer shell electrons experience less of a force of attraction to the nucleus than do the electrons in the inner shells. EXERCISES Ex. 1. Make the following sentences negative. 1. Each basic element has a certain number of electrons and protons, which distinguishes each element from all other basic elements. 2. These materials are called insulators. 3. The third shell can have up to 18 electrons. 4. This way the atom stays electrically balanced. 5. Although electrons are very small, their negative electrical charges are still quite strong. Ex. 2. Make up questions to which the following sentences are the answers. 1. The closest shell to the nucleus can have up to 2 electrons. 2. In most elements, the number of electrons is equal to the number of protons. 3. This positively 7

charged electrostatic field is exactly the same strength as the electrostatic field in an electron, but it is opposite in polarity. 4. Two electrons will tend to repel each other because both have a negative electrical charge. 5. Another important fact about the electrical charges of protons and electrons is that the farther away they are from each other, the less force their electric fields have on each other. 6. Many materials do not have any free electrons. Ex. 3. Translate the sentences using the examples given below. The hypothesis proposed agreed with the experimental observation. -> The hypothesis which is (was) proposed agreed with the experimental observation.  !      +   % . For some time scientists remained interested in the problem. "         +  . 1. The method applied increased the accuracy of the results. 2. After a heated discussion the laboratory applied the method improved by Dr. N. 3. The scientist theoretically predicted complicated interaction between the components involved in the process. 4. At that time the problem presented increased danger of radioactive contamination and encountered opposition at most laboratories concerned. 5. The hypothesis concerned synthesized materials and did not apply to natural products. 6. Heat resistant materials developed in the last decade produced a revolution in a number of industries. 7. Automatized information processing radically modified the method devised. 8. The crystal produced revealed cracked faces. Ex. 4. Identify the element described by which-clause and give Russian equivalents of which. 1. After Von Neuman's tragic death the computer project was abandoned, which was most unfortunate for Princeton. 2. It is impossible to make a complete list of things which physicists may find interesting to do in the coming decade. 3. This idea, which was wrong at that time, is no less wrong today. 4. The other disastrous thing seems to be a real danger, which can be avoided if we stayed diversified. 5. This technique was borrowed from physics, which is rather typical of the presentday biology. 6. The scientists expected the experiment to be completed by the end of the month, which would allow them to participate in the symposium. 7. That this comes out to be the case is a conclusive proof of the correctness of the theory. 8. What is still doubtful is the details, which does not prevent the theory from being useful, however. Ex. 5. Fill in the blanks with the appropriate words from the list given below. 1. The sun … in its axis once every 27 days. 2. The … of light is expressed in meters per second. 3. The … solar day is the average length of the solar days in a 8

year. 4. Hydrogen is the … element in all the stars. 5. If a pound of matter could be entirely converted into energy, the amount of energy would be … to the burning of 1,500,000 tons of coal. 6. The so-called polar wandering in which the earth's … actually remains fixed in its direction in space while the earth's matter moves around it has been explained. 7. Just as … revolve about the sun, there are bodies called moons revolving in orbits about their planets. 8. Mars is very small and its gravitational … is very weak. 9. … are caused by the attraction of the moon. 10. The diameters of these islands … from only a few hundred feet to about ten miles. 1) tides, 2) planets, 3) predominant, 4) equal, 5) range, 6) rotates, 7) pull,  8) axis, 9) speed, 10) mean Ex. 6. Give English equivalents of the sentence using that, which or what. 1. To,  +   ,  . 2. _   ,    +     . 3. _,     ,   *    + . 4. " +    $ ,   *    + . 5. " +     ,    %%  ,     *   +   . 6.      !  ,         . READ THE TEXT THE VALENCE SHELL What is the valence shell? Notice that in the copper atom pictured below the outside shell has only one electron. This represents that the copper atom has one electron that is near the outer portion of the atom. The outer shell of any atom is called the valence shell. When the valence electron in any atom gains sufficient energy from some outside force, it can break away from the parent atom and become what is called a free electron. Atoms with few electrons in their valence shell tend to have more free electrons since these valence electrons are more loosely bound to the nucleus. In some materials like copper, the electrons are so loosely held by the atom and so close to the neighboring atoms that it is difficult to determine which electron belongs to which atom. Under these conditions, the valence or free electrons tend to drift randomly from one atom to its neighboring atoms. Under normal conditions the 9

movement of the electrons is truly random, meaning they are moving in all directions by the same amount. However, if some outside force acts upon the material, this flow of electrons can be directed through materials and this flow is called electrical current. Materials that have free electrons and allow electrical current to flow easily are called conductors. Many materials do not have any free electrons. Because of this fact, they do not tend to share their electrons very easily and do not make good conductors of electrical currents. These materials are called insulators. ELEMENTS Any material that is composed of only one type of atoms is called a chemical element, a basic element, or just an element. Any material that is composed of more than one type of atoms is called a compound. Every element has a unique atomic structure. Scientists know of only about 109 basic elements at this time. (This number has a habit of changing.) All matter is composed of combinations of one or more of these elements. Ninety-two of these basic elements occur naturally on or in the Earth. The other elements are man-made. You may recognize the names of some of these basic elements, such as: hydrogen, helium, oxygen, iron, copper, gold, aluminum, uranium. The periodic table of elements lists the basic elements and some of their properties ͳǤ ‡Ž‡‡–‹•ƒ–‡”‹ƒŽ…‘’‘•‡†‘ˆ‘Ž›‘‡‹†‘ˆƒ–‘Ǥ ʹǤ …‘’‘—†‹•ƒ–‡”‹ƒŽ…‘’‘•‡†‘ˆ‘”‡–Šƒ‘‡‹†‘ˆƒ–‘Ǥ ͵Ǥ ‘‡ ‡šƒ’Ž‡• ‘ˆ ‡Ž‡‡–• –Šƒ– …ƒ „‡ ˆ‘—† ‘ –Š‡ ’‡”‹‘†‹… –ƒ„Ž‡ ƒ”‡ Š›†”‘‰‡ǡŠ‡Ž‹—ǡ‘š›‰‡ǡ‹”‘ǡ…‘’’‡”ǡ‰‘Ž†ǡƒŽ—‹—ǡ—”ƒ‹—Ǥ UNIT 2 Vocabulary list foil 1)   2)  3)   4)   foil paper   investigate 1)   2)   3)    4)   5)  6)  exclude  % (from );   ;   ( !  . . ) deflect 1)    ( )      ( from );   ;     10

deflection 1)   2)   3)  4)  # 5)   Oersted discovered that an electric current would deflect a magnetic needle. – `  ,  +         . This special metal shield will deflect a bullet from its course. – `      #  %  . repel  ,   particles repel one another –     % bounce off  $  - . infinity 1)  ;  to infinity –   Syn: eternity , endlessness 2) - . , ;   ;   fuzzy 1)  2)  3) $ 4) $ 5)  6)  7)   8)   fuzziness )   ,   ,  ;   ,  ,  ; )  !   ;   MODELS OF THE ATOM In the early 1900's many scientists turned their attention to the investigation of the structure of the atom. Many models were proposed, and a handful were adopted as ways to describe the atom. Neither of them was perfect but they have brought us a long way toward understanding of these building blocks. Three of particular interest to us in physics are: 1. The Rutherford Model 2. The Bohr Model 3. The Cloud Model Even though these models are different, neither one excludes the other two. Accepting one model does not cancel out the other two. It is possible to accept all three models at the same time. The Rutherford model In 1909 Ernest Rutherford conducted what is now a famous experiment where he bombarded gold foil with alpha particles (Helium nuclei). A source which underwent alpha decay was placed in a lead box with a small hole in it. Any of the alpha particles which hit the inside of the box were simply stopped by the box. 11

Only those which passed through the opening were allowed to escape, and they followed a straight line to the gold foil.

Observations Most of the alpha particles passed straight through the gold foil. Some of the alpha particles deflected by very small amounts. x A very few deflected greatly. x Even fewer bounced of the foil and back to the left. Considering the deflection of the alpha particle through large angles and even bouncing off the gold foil you must keep in mind that the gold nuclei have a charge of +79 and the alpha particle has a charge of +2. These two positive charges repel each other. The closer they get, the greater the force. The greater the force, the greater the amount of deflection. x x

The Bohr Model While the Rutherford model focused on describing the nucleus, Niels Bohr turned his attention to describing the electron. Prior to the Bohr Model, the accepted model was one which depicted the electron as an orbiting planet. The flaw with the planet-like model is that an electron particle moving in a circular path would be accelerating. An accelerating electron creates a changing magnetic field. This changing magnetic field would carry energy away from the electron, eventually slowing it down and allowing it to be “captured” by the nucleus. 12

Bohr built upon spectroscopic observations of atoms. Spectroscopists noticed that an atom can only absorb certain energies (colors) of light (the absorption spectrum) and, once excited, Absorption Spectrum can only release certain energies (the emission spectrum) and these energies happen to be the same. Bohr used these observations to argue that the energy of a bound electron is “quantized.” Emission Spectrum Quantized is a fancy word meaning only certain quantities of energy are allowed. This explanation addresses the true origin of light. Since only certain energy levels are allowed, it is actually possible to diagram the atom in terms of its energy levels. In the figure below you see a model of a Hydrogen atom and to the right of it, a Bohr energy level diagram.

The Hydrogen Atom

If the energy of the photon of light is just right, it will cause the electron to jump to a higher level. When the electron jumps back down, a photon is created for each jump down. A photon without the right amount of energy passes through the atom with no effect. Photons with too much energy will cause the electron to be ejected, which ionizes the atom. An ionized electron is said to be in the n=infinity energy level. Keep in mind that these rings are not actually orbits, but are levels that represent the location of an electron wave. The number n corresponds to the number of complete waves in the electron.

13

This formula can be used to determine the energy of the photon emitted (+) or absorbed (-).

Ephoton = Einitial - Efinal

Ephoton = hf where h = 6.6 x 10-34 or 4.14 x 10-15 eVs

This formula can be used to determine the energy of a photon if you know its frequency. Planck's Js constant, h, can be used in terms of Joule(s) or eV(s). (note: the Regents reference table only gives it in terms of Js)

EXERCISES Ex. 1. Make the following sentences negative. 1. We will limit our discussions to protons, neutrons and electrons. 2. Protons and neutrons are believed to be made up of even smaller particles called quarks. 3. The electrons actually change their orbit with each revolution. 4. Quantized is a fancy word meaning that only certain quantities of energy are allowed. 5. The number n corresponds to the number of complete waves in the electron. Ex. 2. Make up questions to which the following sentences are the answers. 1. Photons with too much energy will cause the electron to be ejected which ionizes the atom. 2. The number n corresponds to the number of complete waves in the electron. 3. He developed the probability function for the Hydrogen atom. 4. The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going. 5. The nucleus is made up of positively charged particles called protons and neutrons which are neutral. 6. Prior to the Bohr Model, the accepted model was one which depicted the electron as an orbiting planet. Ex. 3 Translate the sentences using the examples given below. The institute installed modernized equipment. "     . The equipment installed modernized our laboratory too. ~      $ %. 14

A. 1.The Conference attended by scientists from different countries discussed new trends and methods in this field of research. 2. One of the rights enjoyed by University scientists is that of combining research with teaching. 3. The discovery followed by further experimental work stimulated research in this area. B. 1. Mathematics, mechanics, statics and geometrical optics referred to as classical disciplines started mathematical traditions in the history of natural science. 2. The heads of the laboratories were asked questions formulated and agreed upon by a group of sociologists. 3. The scientist's eloquence substituted for logical argu-entation in defending an “extreme” viewpoint failed to win the audience. 4. The mixture allowed to stay overnight gradually decomposed. 5. Physicists showed that particles thought of as “elementary” were in fact “nonelementary”. 6. The subjects dealt with under this topic aroused a heated discussion. Ex. 4. Identify the structures including what and give Russian equivalents of the relevant part of the sentence. 1. What is done cannot be undone. 2. I would here refer to what I have already said about these substances. 3. This article will review what has been achieved in this field since 1981. 4. From what has been said one concludes that the results obtained depend principally on the technique employed. 5. What we want to stress is indivisibility and complexity of the environment. 6. What follows is extremely significant in its bearing on the problem of the relationship of physics with other sciences. 7. Much of what we do in space, much of what is expected of us strains our technology to the breaking point. 8. In this article Dyson states what may be considered three rules of managing a research laboratory. 9. What goes into a system must eventually come out. Ex. 5. Learn to distinguish between modal and auxilliary to have and to be. State their function and give Russian equivalents. 1. The argument is that by that time the resources of the plane may have been exhausted and man may have had to leave the Earth in search for another habitable place. 2. To get anywhere and back in a lifetime the speed would have to be very high so as to take advantage of the relativistic change in clock rates. 3. The maximum value which is to be expected is only reached in the range of variables used in the tests. 4. If Mars were a testing ground for our notion about the origin of life, we must avoid using the same notion to conclude in advance that Mars is lifeless. 5. As it is true of the author, we have had to be a little arbitrary in deciding what to include and what to omit. 6. If we built a scale model with the Earth as a ball 100 feet in diameter, this ocean would be less than half an inch deep. 15

The Cloud Model Erwin Schredinger built upon the thoughts of Bohr yet took them in a new direction. He developed the probability function for the Hydrogen atom (and a few others). The probability function basically describes a cloudlike region where the electron is likely to be found. It cannot say with any certainty, where the electron actually is at any point in time, yet can describe where it ought to be. Clarity through fuzziness, is one way to describe the idea. The model based on this probability equation can best be described as the cloud model. The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going. The red dot in the middle represents the nucleus while the red dot around the outside represents an instance of the electron. Imagine, as the electron moves it leaves a trace of where it was. This collection of traces quickly begins to resemble a cloud. The probable locations of the electron predicted by Schredinger's equation happen to coincide with the locations specified in Bohr's model. Whatisanatomcomposedof?  An atom is the smallest particle of any element that still retains the characteristics of that element. However, atoms consist of even smaller particles. Atoms consist of a central, dense nucleus that is surrounded by one or more lightweight negatively charged particles called electrons. The nucleus is made up of positively charged particles called protons and neutrons which are neutral. An atom is held together by forces of attraction between the electrons and the protons. The neutrons help to hold the protons together. Protons and neutrons are believed to be made up of even smaller particles called quarks. We will limit our discussions to protons, neutrons and electrons. Niels Bohr was a Danish scientist who introduced the model of an atom in 1913. Bohr's model consists of a central nucleus surrounded by tiny particles called 16

electrons that are orbiting the nucleus in a cloud. These electrons are spinning so fast around the nucleus of the atom that they would be just a blur if we could see particles that small. In our pictures and exercises the electron appears to orbit in the same path around the nucleus much like the planets orbit the Sun. But, please be aware that electrons do not really orbit in the same path. The electrons actually change their orbit with each revolution. UNIT 3 Vocabulary list penetrate 1) )   ,   ,  The water has penetrated into the bedrooms. – "     . These new ideas are penetrating into the framework of society. – `   %  #. penetration 1)  2)   3)  4)   5)   6)    scatter 1)  2)   3)  4)  5)   6) 7)   8) $ scatter electrons  +  scatter plot    breakthrough 1)   /  !;  ( ) 2)    capture 1)  2)  3)  4) ! 5)   6)   capture electron  +  compelling ,  , ,   compelling reason !  attraction 1)   2)  ! 3)  ! attractive interaction   ! Coulomb’s attraction    ! 17

determine 1)   ,   ( # % , !,     . .) to determine the answer to the problem –        THE ATOM By the early 20th century, there was rather compelling evidence that matter could be described by an atomic theory. That is, matter is composed of relatively few building blocks that we refer to as atoms. This theory provided a consistent and unified picture for all known chemical processes at that time. However, some mysteries could not be explained by this atomic theory. In 1896, A.H. Becquerel discovered penetrating radiation. In 1897, J.J. Thomson showed that electrons have negative electric charge and come from ordinary matter. For matter to be electrically neutral, there must also be positive charges lurking somewhere. Where are and what carries these positive charges? A monumental breakthrough came in 1911 when Ernest Rutherford and his coworkers conducted an experiment intended to determine the angles through which a beam of alpha particles (helium nuclei) would scatter after passing through a thin foil of gold.

Models of the atom. The dot at the center of the Rutherford atom is the nucleus. The size of the dot is enlarged so that it can be seen in the figure. What results would be expected for such an experiment? It depends on how the atom is organized. A prevailing model of the atom at the time (the Thomson, or “plum-pudding,” atom) proposed that the negatively charged electrons (the plums) were mixed with smeared-out positive charges (the pudding). This model explained the neutrality of bulk material, yet still allowed the description of the flow of electric charges. In this model, it would be very unlikely for an alpha particle to scatter through an angle greater than a small fraction of a degree, and the vast majority should undergo almost no scattering at all. 18

The results from Rutherford’s experiment were astounding. The vast majority of alpha particles behaved as expected, and hardly scattered at all. But there were alpha particles that scattered through angles greater than 90 degrees, incredible in light of expectations for a “plum-pudding” atom. It was largely the evidence from this type of experiment that led to the model of the atom as having a nucleus. The only model of the atom consistent with this Rutherford experiment is that a small central core (the nucleus) houses the positive charge and most of the mass of the atom, while the majority of the atom’s volume contains discrete electrons orbiting about the central nucleus. Under classical electromagnetic theory, a charge that is moving in a circular path, loses energy. In Rutherford’s model, the electrons orbit the nucleus similar to the orbit of planets about the sun. However, under this model, there is nothing to prevent the electrons from losing energy and falling into the nucleus under the influence of its Coulomb attraction. This stability problem was solved by Niels Bohr in 1913 with a new model in which there are particular orbits in which the electrons do not lose energy and therefore do not spiral into the nucleus. This model was the beginning of quantum mechanics, which successfully explains many properties of atoms. Bohr’s model of the atom is still a convenient description of the energy levels of the hydrogen atom. EXERCISES Ex. 1 Make the following sentenses negative. 1. Becquerel decided to develop his photographic plates. 2. In this model, it would be very unlikely for an alpha particle to scatter through an angle greater than a small fraction of a degree. 3. The size of the dot is enlarged so that it can be seen in the figure. 4. The results from Rutherford’s experiment were astounding. 5. By the early 20th century, there was rather compelling evidence that matter could be described by an atomic theory. Ex. 2 Make up questions to which the following sentences are the answers. 1. At high enough energy, the addition of energy creates new particles rather than frees the quarks. 2. Bohr’s model of the atom is still a convenient description of the energy levels of the hydrogen atom. 3. Energy brought into a nucleus to try to separate quarks increases the force between them. 4. This hypothesis was disproved on the 26-27th of February, when his experiment “failed” because it was overcast in Paris. 5. Because gamma rays carry no electric charge, they can penetrate large distances through materials. 6. A sheet of aluminum one millimeter thick or several meters of air will stop these electrons and positrons. 19

Ex. 3 Give Russian equivalents of whether. . . . 1. The question is whether he will send you to the conference or go himself. 2. Whether the project will be approved at present is a matter of importance. 3. One of the fundamental questions is whether petroleum migrated over considerable distances to form pools, or whether it was formed essentially in place. 4. There was a disagreement whether they should continue along the same line or whether they should take another approach. 5. Whether this difference of approach played a decisive role in the final solution to the problem remains a subject for speculation. 6. One of the fundamental problems of today is whether we will be able to meet the challenge of the environmental crisis. Ex. 4. Fill in the blanks with the proper words from the list below 1. World science is faced with the all-important task of finding effective ... of protecting the atmosphere from pollutants. 2. The data available to man concerning the physical phenomena of space might not be very exciting to those who cannot interpret their ... 3. Natural scientists are so interested in their selfmade problems that they tend to neglect the problems that are most . . . for human life. 4. The name atom comes from the Greek word and . . . indivisible. 5. The information on the physical phenomena of space is a part of the answer to space exploration, but is . . . the total explanation 6. Radar techniques have recently been employed to obtain more accurate measurements of the . . . distance between the Earth and the Sun. 7. The main task of ecology is to support survival of plant, animal and human life .... means, meaning, meaningful, means, by no means, by all means, mean. Ex. 5 Translate the sentences into English using who, which, which of, what. 1. _   ,       +. 2. ` ,   . 3. _  ,   +    !. 4. / $ ,      + . 5. _  ,           . 6. /  ,    + . 7. €  , %     + . 8. _   $ ,     . Ex. 6. From the list below choose an adequate English word group to explain the meaning of the italicized words. 1. It took him some time to bring home the fact that the experiment was dangerous. 2. Nowadays most people find it difficult to keep pace with the information accumulated in their special field of interest. 3. It is not quite clear at 20

the moment who will see to it that all is in balance. 4. It is not very wise of you to cut your life short by ignoring your doctor's advice. 5. The problem was to get rid of the unwanted impurities. 6. I don't quite understand what this symbol stands for. 7. It was only in this century that aluminium was produced in quantity. to represent; to make shorter; to make clear; to take care; in large amounts; to remove; to keep up with. The Nucleus The atomic nucleus consists of nucleons–protons and neutrons. Protons and neutrons are made of quarks and held together by the strong force generated by gluon exchange between quarks. In nuclei with many nucleons, the effective strong forces may be described by the exchange of mesons (particles composed of quark-antiquark pairs). A proton consists of two up quarks and one down quark along with short-lived constituents of the strong force field. A neutron is similar except that it has two down quarks and one up quark. Although scientists are convinced that nucleons are composed of quarks, a single quark has never been isolated experimentally. Energy brought into a nucleus to try to separate quarks increases the force between them. At high enough energy, the addition of energy creates new particles rather than frees the quarks. The Discovery of Radioactivity In 1896 Henri Becquerel was using naturally fluorescent minerals to study the properties of x-rays, which had been discovered in 1895 by Wilhelm Roentgen. He exposed potassium uranyl sulfate to sunlight and then placed it on photographic plates wrapped in black paper, believing that the uranium absorbed the sun’s energy and then emitted it as x-rays. This hypothesis was disproved on the 26-27th of February, when his experiment “failed” because it was overcast in Paris. For some reason, Becquerel decided to develop his photographic plates anyway. To his surprise, the images were strong and clear, proving that the uranium emitted radiation without an external source of energy such as the sun. Becquerel discovered radioactivity. Becquerel used an apparatus similar to that displayed below to show that the radiation he discovered could not be x-rays. X-rays are neutral and cannot be bent 21

in a magnetic field. The new radiation was bent by the magnetic field so that the radiation must be charged and different from x-rays. When different radioactive substances were put in the magnetic field, they deflected in different directions or not at all, showing that there were three classes of radioactivity: negative, positive, and electrically neutral l.

Ernest Rutherford, who did many experiments studying the properties of radioactive decay, named these alpha, beta, and gamma particles, and classified them by their ability to penetrate matter. Rutherford used an apparatus similar to that depicted in the figure. When the air from the chamber was removed, the alpha source made a spot on the photographic plate. When air was added, the spot disappeared. Thus, only a few centimeters of air were enough to stop the alpha radiation. Because alpha particles carry more electric charge, are more massive, and move slowly compared to beta and gamma particles, they interact much more easily with matter. Beta particles are much less massive and move faster, but are still electrically charged. A sheet of aluminum one millimeter thick or several meters of air will stop these electrons and positrons. Because gamma rays carry no electric charge, they can penetrate large distances through materials before interacting – several centimeters of lead or a meter of concrete is needed to stop most gamma rays. UNIT 4 Vocabulary list proton accelerator   transform  ;   , %, )    +   (., % +%  + % ) 22

transformation 1)  2) ! 3)   4) # 5)  emit 1)   ,  ,   (,  ,   . .);  ,  ( , , ) the rays of heat that are emitted by the warm earth –    ,     The factory has been emitting black smoke from its chimneys, which is against the law. – 4        , + . half-life 1)   # 2)    3)    half-life-decay  , half-life period    momentum 1)   ! ;  ,   (!#  );  + 2)  ,  ; !#   to gain, gather momentum –  !#%   binding 1. 1)   () 2)  ( % ,  # %  - .   ,   ) Syn: bond, band, bandage, fastening binding energy +  , binding kinetics    bond activation     Beta Decay

Beta particles are electrons or positrons (electrons with positive electric charge, or antielectrons). Beta decay occurs when, in a nucleus with too many protons or too many neutrons, one of the protons or neutrons is transformed into the other. In beta minus decay, a neutron decays into a proton, an electron, and an antineutrino. In beta plus decay, a proton decays into a neutron, a positron, and a neutrino. Both 23

reactions occur because in different regions of the Chart of the Nuclides, one or the other will move the product closer to the region of stability. These particular reactions take place because conservation laws are obeyed. Electric charge conservation requires that if an electrically neutral neutron becomes a positively charged proton, an electrically negative particle (in this case, an ele ctron) must also be produced. Similarly, conservation of lepton number requires that if a neutron (lepton number = 0) decays into a proton (lepton number = 0) and an electron (lepton number = 1), a particle with a lepton number of -1 (in this case an antineutrino) must also be produced. The leptons emitted in beta decay did not exist in the nucleus before the decay – they are created at the instant of the decay. To the best of our knowledge, an isolated proton, a hydrogen nucleus with or without an electron, does not decay. However within a nucleus, the beta decay process can change a proton to a neutron. An isolated neutron is unstable and will decay with a half-life of 10.5 minutes. A neutron in a nucleus will decay if a more stable nucleus results; the half-life of the decay depends on the isotope. If it leads to a more stable nucleus, a proton in a nucleus may capture an electron from the atom (electron capture), and change into a neutron and a neutrino. Proton decay, neutron decay, and electron capture are three ways in which protons can be changed into neutrons or vice-versa; in each decay there is a change in the atomic number, so that the parent and daughter atoms are different elements. In all three processes, the number A of nucleons remains the same, while both proton number, Z, and neutron number, N, increase or decrease by 1. In beta decay the change in the binding energy appears as the mass energy and kinetic energy of the beta particle, the energy of the neutrino, and the kinetic energy of the recoiling daughter nucleus. The energy of an emitted beta particle from a particular decay can take on a range of values because the energy can be shared in many ways among the three particles while still obeying energy and momentum conservation. EXERCISES Ex. 1. Make the following sentences negative. 1. In beta decay the change in the binding energy appears as the mass energy. 2. Many nuclei more massive than lead decay by this method. 3. Because of its smaller mass, most of the kinetic energy goes to the alpha particle. 4. The energy of an emitted beta particle from a particular decay can take on a range of values. 5. A neutron in a nucleus will decay if a more stable nucleus results, the half-life of the decay depends on the isotope. Ex. 2 Make up questions to which the following sentences are the answers. 1. In beta decay the change in binding energy appears as the mass energy and 24

kinetic energy of the beta particle, the energy of the neutrino, and the kinetic energy of the recoiling daughter nucleus. 2. Beta decay occurs when, in a nucleus with too many protons or too many neutrons, one of the protons or neutrons is transformed into the other. 3. Proton decay, neutron decay, and electron capture are three ways in which protons can be changed into neutrons. 4. Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus, bringing it to a more stable configuration. Ex. 3 Translate the following sentences into Russian. 1. For scientific development to be of benefit for man, scientists must occupy themselves with problems that have direct bearing on our lives. 2. Molecular biologists are known to borrow their techniques from other sciences, mainly from physics. 3. How the application of his discovery will affect man is sometimes rather hard for the scientist to foresee. 4. The author devoted a special chapter of his book to what may be expected to dominate the science scene in the near future. 5. The method of inductive reasoning known to be established by Bacon leads from observation to general laws. 6. His idea was fruitful enough for others to take it up and develop it further. 7. For an original idea to be a product of one man's genius is quite natural. But for an idea to be transformed into a product, many people's effort is required. Ex. 4. Translate the following sentences into English. 1. 9   +  . 2. 4 !  %    +  . 3. ‚ ! ! ,   . 4. „      . 5. /    ,   #. 6. ',         . 7. /,      . 8. &         %,   !    . Ex. 5 Fill in the blanks with the appropriate words from the list given below. 1. Mankind is known to be most intimately … nature. 2. Is it difficult to … one state of matter … another? 3. Atoms can be neutral and positively or negatively …. 4. If an atom … one or more electrons, a negative ion is formed. 5. Antimatter is composed of antiatoms made of negative …. at their centers and positive electrons, moving around them. 6. Because protons … each other the nuclei should fly apart, but they do not. 7. The most characteristic thing about meteorites is that they possess compounds of carbon with metals, which are … carbides. 8. If the earth's …, were entirely iron, its total quantity within the whole earth would be at least 35 per cent. 9. Let us … that these angles are equal. 10. Living things are 25

not always easy to … from non-living ones, and we should therefore know the characteristics which indicate that a thing is alive. a) charged, b) assume; c) tell from, d) nuclei, e) additional, f) distinguish, g) gains, h) called, i) associated with, j) core, k) repel ALPHA DECAY

In alpha decay the nucleus emits a 4He nucleus, an alpha particle. Alpha decay occurs most often in massive nuclei that have too large a proton to neutron ratio. An alpha particle, with its two protons and two neutrons, is a very stable configuration of particles. Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus, bringing it to a more stable configuration. Many nuclei more massive than lead decay by this method. Consider the example of 210Po decaying by the emission of an alpha particle. The reaction can be written 210Po † 206Pb + 4He. This polonium nucleus has 84 protons and 126 neutrons. The ratio of pr otons to neutrons is Z/N = 84/126, or 0.667. A 206 Pb nucleus has 82 protons and 124 neutrons, which gives a ratio of 82/124, or 0.661. This small change in the Z/N ratio is enough to put the nucleus into a more stable state, and as shown in the figure, brings the "daughter" nucleus (decay product) into the region of stable nuclei in the Chart of the Nuclides. In alpha decay, the atomic number changes, so the original (or parent) atoms and the decay-product (or daughter) atoms are different elements and therefore have different chemical properties.

Upper end of the Chart of the Nuclides In the alpha decay of a nucleus, the change in binding energy appears as the kinetic energy of the alpha particle and the daughter nucleus. Because this energy must be shared between these two particles, and because the alpha particle and 26

daughter nucleus must have equal and opposite momenta, the emitted alpha particle and recoiling nucleus will each have a well-defined energy after the decay. Because of its smaller mass, most of the kinetic energy goes to the alpha particle. UNIT 5 Vocabulary list short-lived 1) !# 2)  3)   4)   5)  short-lived isotope !# , short-lived radiation   !#  fission 1. 1)  ,    ,   - binary fission Syn: splitting 1. 2) # ,         – nuclear fission 3)   . 2. 1)   ,    2) ) #   ,   (    ) )  # ,   (  ) approximately 1) c 2)    3)  approximately compact set –   ! approximately continuous function –     approximately differentiable function –      RADIOACTIVITY

In radioactive processes, particles or electromagnetic radiation are emitted from the nucleus. The most common forms of radiation emitted have been traditionally classified as alpha (ˆ), beta (‰), and gamma (Š) radiation. Nuclear radiation occurs in other forms, including the emission of protons or neutrons or spontaneous fission of a massive nucleus. Of the nuclei found on Earth, the vast majority are stable. This is so because almost all short-lived radioactive nuclei have decayed during the history of the Earth. There are approximately 270 stable isotopes and 50 naturally occurring radioisotopes (radioactive isotopes). Thousands of other radioisotopes have been made in the laboratory. 27

Radioactive decay will change one nucleus to another if the product nucleus has a greater nuclear binding energy than the initial decaying nucleus. The difference in binding energy (comparing the before and after states) determines which decays are energetically possible and which are not. The excess binding energy appears as kinetic energy or rest mass energy of the decay products. The Chart of the Nuclides, part of which is shown above, is a plot of nuclei as a function of proton number, Z, and neutron number, N. Some stable nuclei and known radioactive nuclei, both naturally occurring and manmade, are shown on this chart, along with their decay properties. Nuclei with an excess of protons or neutrons in comparison with the stable nuclei will decay toward the stable nuclei by changing protons into neutrons or neutrons into protons, or else by shedding neutrons or protons either singly or in combination. Nuclei are also unstable if they are excited, that is, not in their lowest energy states. In this case the nucleus can decay by getting rid of its excess energy without changing Z or N by emitting a gamma ray. Nuclear decay processes must satisfy several conservation laws, meaning that the value of the conserved quantity after the decay, taking into account all the decay products, must equal the same quantity evaluated for the nucleus before the decay. Conserved quantities include total energy (including mass), electric charge, linear and angular momentum, number of nucleons, and lepton number (sum of the number of electrons, neutrinos, positrons and antineutrinos – with antiparticles counting as -1).

28

137Ba decay data, counting numbers of decays observed in 30-second intervals. The best-fit exponential curve is shown. The points do not fall exactly because of statistical counting fluctuations The probability that a particular nucleus will undergo radioactive decay during a fixed length of time does not depend on the age of the nucleus or how it was created. Although the exact lifetime of one particular nucleus cannot be predicted, the mean (or average) lifetime of a sample containing many nuclei of the same isotope can be predicted and measured. A convenient way of determining the lifetime of an isotope is to measure how long it takes for one-half of the nuclei in a sample to decay – this quantity is called the half-life, t(1/2). Of the original nuclei that did not decay, half will decay if we wait another half-life, leaving one-quarter of the original sample after a total time of two half-lives. After three half-lives, one-eighth of the original sample will remain and so on. Measured half-lives vary from tiny fractions of seconds to billions of years, depending on the isotope. The number of nuclei in a sample that will decay in a given interval of time is proportional to the number of nuclei in the sample. This condition leads to radioactive decay showing itself as an exponential process, as shown above. The number N of the original nuclei remaining after a time t from an original sample of N0 nuclei is N = N0e-(t/T) where T is the mean lifetime of the parent nuclei. From this relation, it can be shown that t(1/2) = 0.693T.

29

EXERCISES Ex. 1 Make the following sentences negative. 1. Nuclear radiation occurs in other forms, including the emission of protons or neutrons. 2. The number of nuclei in a sample that will decay in a given interval of time is proportional to the number of nuclei in the sample. 3. This condition leads to radioactive decay showing itself as an exponential process, as shown above. 4. The best-fit exponential curve is shown. Ex. 2 Make up questions to which the following sentences are the answers. 1. The number of nuclei in a sample that will decay in a given interval of time is proportional to the number of nuclei in the sample. 2. The force between two objects can be described as the exchange of a particle. 3. Nuclei are also unstable if they are excited, that is, not in their lowest energy states. 4. Of the original nuclei that did not decay, half will decay if we wait another half-life, leaving one-quarter of the original sample after a total time of two half-lives. 5. Measured half-lives vary from tiny fractions of seconds to billions of years, depending on the isotope. 6. The points do not fall exactly because of statistical counting fluctuations Ex. 3 Translate the following sentences into Russian. 1. The aim was to discuss the impact of scientific activity on technology. 2. If we are to achieve the aim we must confine our attention to one point only. 3. Perhaps the greatest problem is to get some understanding of the remarkable phenomenon. 4. The original idea was to take advantage of the high temperature of the process. 5. Glass which is to be used for lenses must be almost colourless. 6. The train is to reach its destination in 52 hours. 7. The joint programme of Russian and foreign scientists on space research is to be discussed at the next COSPAR conference. Ex. 4 Translate the following sentences into English. 1. `   $ !,       . 2. '       ,   !  !  . 3. ‹   %  ,        +  . 4. `   . 5. 4    $     ,  + !   . 6.       %,        . 7. &      + +,         +  . 8. 4! $,   ,  . 30

Ex. 5 Fill in the blanks with the appropriate words from the list given below. 1. Alchemists tried to create … from a mixture of common substances. 2. Radioactive elements were found to give off other types of …. 3. Water is … hydrogen and oxygen. 4. A compound is a substance that can be … simpler elements. 5. Different isotopes of hydrogen … the number of neutrons in the nucleus. 6. A light year is actually … the enormous distance which light would travel in a year through the vacuum of interstellar space. 7. Bombarding the nuclei of atoms … the release of atomic energy. 8. Nuclear power stations … the ordinary ones only in the source of heat. 9. ... the Second World War Kurchatov used his energy and experience for the defense of his country. 10. Stars are classified ... their brightness. 1) differ from, 2) radiation, 3) during, 4) resulted in, 5) equal to, 6) vary in, 7) gold, 8) decomposed into, 9) according to, 10) composed of Radioactivity in nature Radioactivity is a natural part of our environment. Present-day Earth contains all the stable chemical elements from the lowest mass (H) to the highest (Pb and Bi). Every element with higher Z than Bi is radioactive. The earth also contains several primordial long-lived radioisotopes that have survived to the present in significant amounts. 40K, with its 1.3 billion year half-life, has the lowest mass of these isotopes and beta decays to both 40Ar and 40Ca. Many isotopes can decay by more than one method. For example, when actinium226 (Z=89) decays, 83% of the rate is through ‰-decay, 17% is through electron capture, and the remainder, 0.006%, is through ˆ-decay. Therefore from 100,000 atoms of actinium, one would measure on average 83,000 beta particles and 6 alpha particles (plus 100,000 neutrinos or antineutrinos). These proportions are known as branching ratios. The branching ratios are different for the different radioactive nuclei. Some radioactive isotopes, for example 14C and 7Be, are produced continuously through reactions of cosmic rays (high energy charged particles from outside the Earth) with molecules in the upper atmosphere. 14C is useful for radioactive dating. Also, the study of radioactivity is very important to understand the structure of the Earth because radioactive decay heats the earth’s interior to very high temperatures.

31

Units of radioactivity The number of decays per second, or activity, from a sample of radioactive nuclei is measured in Becquerel (Bq), after Henri Becquerel. One decay per second equals one Becquerel. An older unit is the Curie, named after Pierre and Marie Curie. One Curie is approximately the activity of 1 gram of radium and equals (exactly) 3.7 x 1010 Becquerel. The activity depends only on the number of decays per second, not on the type of decay, the energy of the decay products, or the biological effects of the radiation. UNIT 6 Vocabulary list single 1)  2)  3)  4)  5)  6)  7)  8)   9)  • consisting of a single element – +  dopee a single crystal –     function of single variable –     single giant pulse – #   , single mass point –   , single operator transformer –   covalent bond     mediate 1)  !  ! 2)  3)  4) ! 5)  !   % transfer 1) ;  ;  ||  ;   ;  2)  3)   ||      coupling constant   coupling with feedback –      % mutual coupling factor – +    FOUR FUNDAMENTAL INTERACTIONS The forces of gravity and electromagnetism are familiar in everyday life. Two new forces are introduced when discussing nuclear phenomena: the strong and weak interactions. When two protons encounter each other, they experience all four of 32

the fundamental forces of nature simultaneously. The weak force governs beta decay and neutrino interactions with nuclei. The strong force, which we generally call the nuclear force, is actually the force that binds quarks together to form baryons (3 quarks) and mesons (a quark and an anti-quark). The nucleons of everyday matter, neutrons and protons, consist of the quark combinations uud and udd, respectively. The symbol u represents a single up quark, while the symbol d represents a single down quark. The force that holds nucleons together to form an atomic nucleus can be thought to be a residual interaction between quarks inside each individual nucleon. This is analogous to what happens in a molecule. The electrons in an atom are bound to its nucleus by electromagnetism: when two atoms are relatively near, there is a residual interaction between the electron clouds that can form a covalent bond. The nucleus can thus be thought of as a “strong force molecule.” The force between two objects can be described as the exchange of a particle. The exchange particle transfers momentum and energy between the two objects, and is said to mediate the interaction. A simple analogue of this is a ball being thrown back and forth between two people. The momentum imparted to the ball by one person gets transferred to the other person when he catches the ball. Table. Strength and range of the four fundamental forces between two protons. Note that the strong force acts between quarks by an exchange of gluons. The residual strong force between two protons can be described by the exchange of a neutral pion. Note, the W± is not included as an exchange particle for the weak interaction because it is not exchanged in the simplest proton-proton interaction. Interaction

Gravity

Weak

Electro-magnetism

Exchange particle Mass mc2 (eV) Coupling constant C2 (J·m) Range (m)

Graviton 0 1.87x10-64

Z0 91x109 3.22x10-31

Photon 0 2.31x10-28

Strong Residual Pion 135x106 2.5x10-27

infinity

2x10-18

infinity

1.5x10-15

The table shows a comparison between the coupling constants and ranges of the four forces acting between two protons. Although the graviton has not yet been observed, it is thought that there is an exchange particle associated with gravity and that eventually gravity will be described in a unified theory with the other three forces of nature. The range of the gravitational and electromagnetic forces is infinite, while that of the strong and weak forces is very short. 33

EXERCISES Ex. 1 Make the following sentences negative. 1. The range of the gravitational and electromagnetic forces is infinite. 2. Other health effects from Chernobyl have been convincingly established. 3. However, it is too soon for them to have been fully manifested. 4. The exchange particle transfers momentum and energy between the two objects. 5. The weak force governs beta decay and neutrino interactions with nuclei. Ex. 2 Make up questions to which the following sentences are the answers. 1. The force between two objects can be described as the exchange of a particle. 2. Gravity will be described in a unified theory with the other three forces of nature. 3. The momentum imparted to the ball by one person gets transferred to the other person when he catches the ball. 4. The nucleons of everyday matter, neutrons and protons, consist of the quark combinations uud and udd. 5. The excess binding energy appears as kinetic energy or rest mass energy of the decay products. Ex. 3. Substitute the proper nouns for the italicized pronouns. 1. Physicists may also be mentioned in this connection but without distinguishing between the practical and theoretical ones. 2. A great deal of attention has been devoted to problems generated by the information explosion as it has been popularly termed. 3. One famous question was already raised: that of the “mathematical dream”. 4. The telescope admitted a hundred times as much light as the unaided human eye, and according to Galileo, it showed an object at fifty miles as clearly as if it was only five miles away. 5. The most wonderful instincts are those of the hive-bee and of the ant. Ex. 4. Identify the function of that (those) and give Russian equivalents of the italicized words. 1. It will be better to say that fundamental research is that which may have no immediate practical value. 2. The task of theory is to enable one to calculate the result of an experiment in a shorter time than that required to perform the experiment. 4. Those interested in the problem are referred to a more recent and complete work by Dr. N. 5. The experimental results indicated the presence of some foreign species and that confirmed an earlier idea concerning the reaction mechanism. 34

Ex. 5 From the list below choose the proper English equivalents of the italicized words. 1. " 1959 .        « %»  «,      ». 2. `      XVII ,       . 3. "          3    . 4. "         3    . 5. =   $  !      . 6. "        1012    . 7.  $    ,     . as many as; as late as; as far as; as few as; as little as; as much as; as early as. NUCLEAR REACTOR ACCIDENTS The accidents at the Three Mile Island (TMI) and Chernobyl nuclear reactors have triggered particularly intense concern about radiation hazards. The TMI accident, in Pennsylvania in 1979, resulted from a combination of deficient equipment and operator errors. Even though there was severe damage to the nuclear fuel within the reactor, very little radioactivity escaped into the outside environment. The effectiveness of the large concrete containment building that surrounded the reactor contributed to this relatively small release. Subsequent studies concluded that the maximum dose received by any member of the public was under 1 mSv (100 mrem). The collective off-site dose is estimated to have been about 20 person-Sv. Under the standard low-dose assumption, this corresponds to one eventual cancer fatality in the neighboring population of 2 million people. (This population receives an annual collective dose of about 6000 person-Sv from natural sources.) The 1986 Chernobyl accident was far more serious. It occurred in a reactor with an unsafe reactor design unique to the Soviet Union. The reactor had no effective containment, and there was a very large release of radionuclides to the environment. The accident led to the death within several months of 31 reactor personnel and firefighters – 28 from a combination of radiation effects and burns from fire, 2 from other injuries, and one from a heart attack. A total of 237 workers were hospitalized for symptoms of radiation sickness, including the 28 who died. A 1996 summary reported an additional 14 deaths among the more severely exposed workers, but it is not clear that these deaths were all due to the prior exposure. There is strong evidence of a substantial increase in thyroid cancers among children living in the vicinity. No other health effects from Chernobyl have been 35

convincingly established. However, it is too soon for them to have been fully manifested. Standard calculations of radiation effects predict that there will be a large number of excess cancer deaths among the so-called “liquidators,” who were engaged in cleanup operations after the accident, as well as in the neighboring population. Considering impacts at greater distances, one early study estimated that the collective dose in the Northern Hemisphere over a 50-year period would be about 930,000 person-Sv. While there is substantial uncertainty in the dose estimate, there is even greater uncertainty as to the impact. If one accepts the linearity hypothesis and assumes 0.05 fatalities per Sv, this dose corresponds to 47,000 eventual cancer fatalities. About 29,000 of these fatalities would occur in Europe (outside the former Soviet Union) due to a cumulative collective dose of 580,000 Sv–an average individual lifetime dose of 1.2 mSv for 490 million people. Given these low average doses, any estimate of predicted deaths from Chernobyl is highly speculative. The deaths will not be identifiable, being masked by the 88,000,000 “normal” cancer fatalities expected in this region during the 50-year period. UNIT 7 Vocabulary list reflection 1) ) , ! (    . .) She stared at her reflection in the mirror. –      !   . Syn: image 1. ) ! (,  , );  ,  the reflection of beam of light off a mirror – !       Reflexion of sound is familiarly illustrated by the echo. – !    %       +. angle of reflection –  ! consequence 1) () ,   (- ) to take, accept, bear, face, suffer the consequences of –  ,      distinguish 1)   ;   ,  I could hardly distinguish anything in the morning mist. –          . Syn: recognize 2) )   ,    ,   ,  (! - . - among / between / from) vehicle 1) )   (!.   ) to drive, operate a vehicle –   - .  , all-purpose 36

vehicle –    ! , hired vehicle, rented vehicle, self-drive vehicle –  , space vehicle –   , armored vehicle –   halftracked vehicle –  off-road vehicle – !  , passenger vehicle— !  CHARGE, PARITY, AND TIME REVERSAL (CPT) SYMMETRY Three other symmetry principles important in nuclear science are parity P, time reversal invariance T, and charge conjugation C. They deal with the questions, respectively, of whether a nucleus behaves in a different way if its spatial configuration is reversed (P), if the direction of time is made to run backwards instead of forward (T), or if the matter particles of the nucleus are changed to antimatter (C). All charged particles with spin 1/2 (electrons, quarks, etc.) have antimatter counterparts of opposite charge and of opposite parity. Particle and antiparticle, when they come together, can annihilate, disappearing and releasing their total mass energy in some other form, most often gamma rays. The changes in symmetry properties can be thought of as “mirrors” in which some property of the nucleus (space, time, or charge) is reflected or reversed. A real mirror reflection provides a concrete example of this because mirror reflection reverses the space direction perpendicular to the plane of the mirror. As a consequence, the mirror image of a right-handed glove is a left-handed glove. This is in effect a parity transformation (although a true P transformation should reverse all three spatial axes instead of only one). Until 1957 it was believed that the laws of physics were invariant under parity transformations and that no physics experiment could show a preference for lefthandedness or right-handedness. Inversion, or mirror, symmetry was expected of nature. It came as some surprise that parity, P, symmetry is broken by the radioactive decay – beta decay process. C. S. Wu and her collaborators found that when a specific nucleus was placed in a magnetic field, electrons from the beta decay were preferentially emitted in the direction opposite to that of the aligned angular momentum of the nucleus. When it is possible to distinguish these two cases in a mirror, parity is not conserved. As a result, the world we live in is distinguishable from its mirror image.

37

The figure above illustrates this situation. The direction of the emitted electron (arrow) reverses on mirror reflection, but the direction of rotation (angular momentum) is not changed. Thus the nucleus before the mirror represents the actual directional preference, while its mirror reflection represents a directional preference not found in nature. A physics experiment can therefore distinguish between the object and its mirror image. If, however, we made a nucleus out of antimatter (antiprotons and antineutrons), its beta decay would behave in the same way, except that the mirror image would represent the preferred direction of electron emission, while the antinucleus in front of the mirror would represent a directional preference not found in nature. The great physicist, Richard Feynman, told a story to illustrate this point: suppose you were in two-way contact with some alien species, but only by “telegraph” (i.e., light flashes or radio signals). The well known procedures of SETI (Search for Extraterrestrial Intelligence), starting with prime numbers and progressing to pictures, physics, and chemistry information could be used to develop a common language and arrive at a good level of communication. You could tell the alien how tall you are by expressing your height in mutually understood wavelengths of light. You could tell the alien how old you are as some large number of ticks of a light-frequency clock. Now you want to explain how humans shake hands when they meet, and you describe extending your right hand. “Wait a moment!” says the alien, “What do you mean by ‘right’?” Until 1957 there would have been no way of answering that question. But now you could use the parity experiment shown in the figure. You could tell the alien to turn the experiment until the electrons come out in the upward direction (the direction opposite gravity), and the front edge of the rotating nucleus will move from right to left or clockwise to make the angular momentum. This works because the parity violation of the weak interaction allows us, at a fundamental level, to distinguish right from left. 38

Feynman also had a punch line to this story. Suppose, after lots of communications you finally can go into space and meet your alien counterpart. If, as you approach one another, the alien extends its left hand to shake, watch out! He is made of antimatter! This, of course, is because a parity violation experiment constructed of antimatter would give the opposite result. If the mirror in the figure not only reversed spatial direction but also changed matter to antimatter, then the experiment in front of the mirror would look just like its mirror image. Changing both C and P preserves the symmetry and we call this CP symmetry. The separate violations of P symmetry and C symmetry cancel to preserve CP symmetry. These symmetry violations arise only from the weak interaction, not from the strong and electromagnetic interactions, and therefore show up strongly only in beta decay. There are fundamental reasons for expecting that nature at a minimum has CPT symmetry – that no asymmetries will be found after reversing charge, space, and time. Therefore, CP symmetry implies T symmetry (or time-reversal invariance). One can demonstrate this symmetry by asking the following question. Suppose you had a movie of some physical process. If the movie were run backwards through the projector, could you tell from the images on the screen that the movie was running backwards? Clearly in everyday life there would be no problem in telling the difference. A movie of a street scene, an egg hitting the floor or a dive into a swimming pool has an obvious “time arrow” pointing from the past to the future. But at the atomic level there are no obvious clues to time direction. An electron orbiting an atom or even making a quantum jump to produce a photon looks like a valid physical process in either time direction. The everyday “arrow of time” does not seem to have a counterpart in the microscopic world – a problem for which physics currently has no answer. Until 1964 it was thought that the combination CP was a valid symmetry of the Universe. That year, Christenson, Cronin, Fitch and Turlay observed the decay of the long-lived neutral K meson. Nuclear physicists conducted many investigations searching for similar T violations in nuclear decays and reactions, but at this time none have been found. This may change soon. Time reversal invariance implies that the neutron can have no electric dipole moment, a property implying separation of internal charges and an external electric field with its lines in loops like Earth’s magnetic field. Currently ultracold neutrons are being used to make very sensitive tests of the neutron’s electric dipole moment, and it is anticipated that a nonzero value may be found within the next few years. 39

EXERCISES Ex. 1 Make the following sentences negative. 1. A movie of a street scene, an egg hitting the floor or a dive into a swimming pool has an obvious “time arrow” pointing from the past to the future. 2. This works because the parity violation of the weak interaction allows us, at a fundamental level, to distinguish right from left. 3. If, however, we made a nucleus out of antimatter (antiprotons and antineutrons), its beta decay would behave in the same way. 4. A physics experiment can therefore distinguish between the object and its mirror image. 5. When it is possible to distinguish these two cases in a mirror, parity is not conserved. Ex. 2 Make up questions to which the following sentences are the answers. 1. It is anticipated that a nonzero value may be found within the next few years. 2. This may change soon. 3. The everyday “arrow of time” does not seem to have a counterpart in the microscopic world. 4. There are fundamental reasons for expecting that nature at a minimum has CPT symmetry. 5. Feynman also had a punch line to this story. 6. Ultracold neutrons are being used to make very sensitive tests of the neutron’s electric dipole moment. 7. You could tell the alien how tall you are by expressing your height in mutually understood wavelengths of light. 8. A real mirror reflection provides a concrete example of this because mirror reflection reverses the space direction perpendicular to the plane of the mirror. Ex. 3. Give Russian equivalents of the italicized words. 1. When it is said that a man weighs 160 lbs, it means that he is exerting a force of 160 lbs on the floor. 2. It is likely that the reserves of oil and coal will be exhausted in less than a century. 3. Lack of figures may make it difficult to produce accurate statistics. 4. In any case it is not difficult to devise a suitable computational scheme. 5. We found it more convenient to describe the structure in terms of bond angles and bond distances. Ex. 4. From the lists below choose the proper English equivalents of italicized words. A. 1. `         #   . 2. &                +. 3. &   ,   40

 !   !        . 4. / !   $% +      . 5.    ,  !. for a long time; before long; long before; as long as; long. Ex. 5. Identify the element intensified by means of "very" and give Russian equivalent of very. 1. The discovery came at the very time when most researchers engaged in the work were about to give it up. 2. All this has been done for the very opposite reason. 3. The experimental approach is very nearly the same as that introduced in the seventies. 4. Such studies require very detailed information concerning the processes at work. MATTER AND ANTIMATTER Time-reversal invariance and the CP violation are connected to another asymmetry of the universe, the imbalance between matter and antimatter. At the microscopic level, matter and antimatter are always created together in 1:1 correspondence. High energy collisions produce equal numbers of quarks and antiquarks. And yet, our universe has a conspicuous surplus of matter, of which we and our surroundings are made. How did this happen? A clue to this deep mystery is provided by the CP violation in the Ko meson, which shows decay modes having a preference for matter over antimatter. The Ko does not have enough mass for its decay to produce protons, but its decay asymmetry suggests that some more massive particle, perhaps a Bo meson containing a bottom quark, might in the early universe have decayed preferentially into protons rather than antiprotons, leading to the present day dominance of matter. Future experiments using the B-Factory, presently under construction at the Stanford Linear Accelerator Center (SLAC), will investigate this problem. Antimatter exists in nature only in the form of antiprotons present in very small numbers in cosmic rays and in positrons (antimatter electrons) produced in some radioactive decays. Recently, evidence has also been found for a “fountain” of positrons ejected from some object near the center of our galaxy, presumably a black hole. However, we are getting better and better at producing and storing antimatter in the laboratory. Antiprotons, antineutrons, and even antideuterons (a nucleus consisting of an antineutron and an antiproton) are routinely produced using high 41

energy particle accelerators at Fermilab in Illinois and CERN in Geneva, Switzerland. Positrons and antiprotons have been trapped in electric and magnetic fields and held under high vacuum for several months. Recently, “antihydrogen” atoms having a positron orbiting an antiproton have been formed in laboratory experiments. These researchers are looking for any indication that trapped positrons, antiprotons, and antihydrogen atoms show a behavior that differs in any way from that of their normal matter counterparts, because any such difference would represent a violation of CPT symmetry. Antimatter nuclei are also interesting for other reasons. Special facilities at CERN and Fermilab provide beams of low energy antiprotons and permit nuclear scientists to study the interactions of antiprotons with matter. While a positron and an electron usually annihilate to form a pair of gamma-ray photons traveling in opposite directions, the annihilation of an antiproton with a proton is more complicated. Several mesons are usually produced. About a third of the mass energy of the proton-antiproton pair becomes inaccessible in the form of energetic neutrinos. Nevertheless, antimatter can be viewed as an extremely compact form of stored energy that can be released by annihilation with matter. The US Air Force has commissioned design studies of antimatter-powered space vehicles that, given a supply of antimatter, look quite feasible. The problem with such schemes is that production of any significant quantity of antimatter would cost far too much right now to be economically feasible. UNIT 8 Vocabulary list experimental technique  + ission product    feasible 1)  ,  , # (  ,   ) Syn: workable, executable, accomplishable, possible, practicable 2)  #,  3)  , !,  (  !, , , ) the only feasible theory –  !  ! interfere 1)   2) $  3)  4) $ 42

artificial 1)  2)  3) $  4)  alpha bombardment   -  precursor , $ debris 1) )  ,  ; ;  Syn: waste )  ,  (- .  , ) Syn: ruins 2)    Syn: waste 3)   ;  , %# !;   recoil atom   cross section of target –  #   + electrons bombard target – +  % $ target atom  $ identification 1) ) ! ; ,  to make an identification – !  positive identification –     !   ;  !    production reactor $    THE SEARCH FOR “HEAVY” ELEMENTS When a nucleus captures a neutron, it often tries to correct for its neutron excess by beta decay, turning a neutron into a proton and thus creating an atom with atomic number Z increased by one unit. This commonly observed phenomenon suggests a way to create new elements of increased atomic number and thus to create ever more massive elements that are not found on Earth. Most of these elements are radioactive, with very short half-lives. However, theories of nuclear structure predict that at a certain atomic number, which is currently beyond present experimental limits, new long-lived nuclei can be created. The most massive naturally occurring element on Earth is uranium (U), with a nucleus of 92 protons. In 1934, scientists started the search for more massive elements with 93 or more protons. They succeeded in 1940 when neptunium (Np, Z = 93) was synthesized at the University of California, Berkeley. Edwin McMillan and Philip Abelson observed Np while studying fission products produced in the bombardment of 238U with thermal neutrons. They found a radioactive reaction product that was not a fission product. McMillan and Abelson 43

chemically separated this new element, Np, from the interfering fission products and chemically identified it as neptunium. Since this breakthrough discovery, scientists from all over the world have been trying to discover ever more massive artificially produced elements. Plutonium (Pu, Z = 94) was discovered in 1941 by bombarding a uranium target with deuterons (a hydrogen nucleus with one proton and one neutron) in the 60Inch Cyclotron at Berkeley. Glenn Seaborg, Arthur Wahl and Joseph Kennedy chemically separated neptunium from the target and detected alpha particles from the plutonium daughter nuclei. Once 239Pu was discovered, there was the potential for using it as a new target to produce more massive elements. After bombardment the material was sent to the Metallurgical Laboratory at the University of Chicago for chemical separation and identification of the new element. 242Cm decays to 238Pu by emitting alpha particles. The identification of curium was possible because the alpha decay of the daughter nucleus, 238Pu, was already known and could be used as a signature for the identification of the curium precursor. The discovery of americium (Am, Z = 95) soon followed when a 239Pu target was bombarded with thermal neutrons in a nuclear reactor. Plutonium captured several neutrons and ultimately became americium. Americium was chemically separated from plutonium and further identified by observing its beta decay to the known 242 Cm isotope. Once americium and curium were discovered and isolated in macroscopic amounts, they were used as targets to produce more massive elements through particle bombardments. Berkelium (Bk, Z = 97) was produced by bombarding milligram quantities of americium with helium ions. Rapid chemical techniques were developed in order to separate and identify this new short-lived element. Likewise, californium (Cf, Z = 98) was produced in a helium bombardment of a target made of microgram amounts of curium. The identification of this element was accomplished with only the 5000 atoms produced in this experiment. The next two elements, einsteinium (Es, Z = 99) and fermium (Fm, Z = 100), were unexpectedly found in the debris from the “Mike” thermonuclear explosion that took place in the Pacific Ocean in 1952. Debris from the explosion was collected and analyzed at several laboratories, and the new elements were discovered in chemical separations of the material. Scientists explained the production of einsteinium and fermium through multiple neutron captures by the uranium used in the thermonuclear device followed by several successive beta decays, which ultimately resulted in atoms with atomic numbers 99 and 100. The last three elements in the actinide series are mendelevium (Md, Z = 101), 44

nobelium (No, Z = 102) and lawrencium (Lr, Z = 103). Mendelevium was truly a unique discovery because the new element was produced and identified virtually one atom at a time. Einsteinium was bombarded with helium ions to produce mendelevium. The production of mendelevium was estimated to be only a few atoms per experiment. The reaction products from the bombardment were collected on thin gold foils that were dissolved in an acid solution, and then chemically treated in order to separate and identify the Md atoms. This is commonly called the recoil method, and is used when small amounts of atoms are produced. The discovery of nobelium was controversial. A team of scientists from several different laboratories claimed discovery in 1957. However, scientists from the United States and the Soviet Union could not confirm their findings. The original claim was proven to be false; the product that was thought to be nobelium was actually something completely different. Nobelium was finally produced and positively identified in 1958. The first identification of lawrencium was made at the Berkeley Lab’s Heavy Ion Linear Accelerator (HILAC) in 1961. Several targets of californium isotopes were bombarded with beams of boron. The reaction products were collected on a mylar tape and moved past a series of alpha detectors. The element lawrencium was identified on the basis of the known alpha decays of its descendant nuclei. Once the actinide series was filled in the periodic table, work was started to produce the transactinide elements. The most recent version of the periodic table includes transactinide elements from rutherfordium (Rf, Z = 104) to element 112, which has not yet been named. As scientists tried to discover and identify the transactinide elements, they encountered several problems that made their task extremely difficult. The rates for producing these elements in accelerator bombardments were incredibly low. Consequently, only a few atoms could be produced over the course of the entire experiment. Sometimes these experiments went on continuously for several weeks. In addition, the half-lives of the transactinides are very short, making their identification a difficult challenge. Unlike neptunium and plutonium, these elements may undergo radioactive decay before being detected. As a result, chemical separations are generally very difficult to perform for identifying transactinides. In order to confirm that a new element has actually been made, members of its decay chain must be detected and traced back as a signature to the unknown element. Elements 104 through 112 were discovered by observing the decay chain of their descendant nuclei. Only a few atoms of these new elements were produced in each experiment. The atoms were isolated from the target and beam material by using a 45

particle separator which separates atoms based on their different masses. The atoms were then allowed to decay and the subsequent alpha particle decay products from the descendant nuclei were correlated to identify the unknown parent nucleus. In the discovery of element 112, the individual atoms were identified by the decay chains of parent-daughter-granddaughter nuclei (above). Different combinations of target and projectile were used in accelerators to produce these new elements. Rutherfordium (104), dubnium (105), and seaborgium (106) were synthesized and identified at Berkeley. Bohrium (107), hassium (108), and meitnerium (109) were synthesized and identified in the early 1980s at the Gesellschaft für Schwerionenforschung (GSI) laboratory near Darmstadt, Germany. In the 1990s, unnamed element 110 was identified at the GSI, Berkeley, and Dubna laboratories, and elements 111 and 112 were found at the GSI laboratory. The names for these new elements are under discussion. New experimental techniques and apparatus are being developed for scientists to extend the periodic table to even more massive elements. A more efficient particle separator will use magnetic fields to separate atoms based on their mass and charge. This equipment will allow detection of nuclides with low production rates and extremely short half-lives. There are plans for using such a separator to produce elements 114 and 116. The present limits for discovering new elements are based on the low production rates and short half-lives. The hope is that new development in detection equipment will increase the sensitivity for detecting fewer atoms (or even a single atom) with very short half-lives. A widely used theory predicts the existence of elements up to Z = 125. In this model, more massive elements would be so unstable that their nuclei would immediately fly apart into nucleons and nuclear fragments and never become atoms. Traditionally, the discoverers of a new element chose its name. Then the International Union of Pure and Applied Chemistry (IUPAC) officially approves the proposed name. However, for several of the transfermium elements (Z = 102 and higher) there had been competing claims to their discovery. Recently, the names for elements have been decided up to Z = 109. It has been possible to study the chemical properties on the macroscopic scale for elements as massive as einsteinium (element 99) and on the tracer scale for elements as massive as seaborgium (element 106). The elements beyond the actinides in the Periodic Table are termed the “transactinides’ and are shown in a Modern Periodic Table with all of the undiscovered elements through number 118 in their expected places. 46

Table

“Heavy” element names that are approved by IUPAC Element Number

IUPAC Proposal

Symbol

101

Mendelevium

Md

102

Nobelium

No

103

Lawrencium

Lr

104

Rutherfordium

Rf

105

Dubnium

Db

106

Seaborgium

Sg

107

Bohrium

Bh

108

Hassium

Hs

109

Meitnerium

Mt

The yields of the most massive elements produced in bombardments of target nuclei with “heavy” ions become extremely small with increasing atomic number, dropping to as little as one atom per week of bombardment for elements as massive as atomic number 112. The half-lives decrease into the millisecond and the microsecond range so that identification of the new nuclei becomes increasingly difficult. These half-lives would be impossibly short were it not for the presence of closed shells of nucleons to increase nuclear stability. It will surely be possible to study the macroscopic properties of fermium (element 100) and not out of the question that this will eventually be done for mendelevium (element 101). The art of one-atom-at-a-time chemistry will advance far beyond what can be imagined today to make it possible to study the chemistry of most massive elements. All of this will result in the delineation of relativistic effects on the chemical properties of these very massive elements, which might thus be substantially different from those expected by simple extrapolation from their less massive homologues in the Periodic Table. EXERCISES Ex. 1 Make the following sentences negative. 1. The present limits for discovering new elements are based on the low production rates and short half-lives. 2. The rates for producing these elements in 47

accelerator bombardments were incredibly low. 3. It has been possible to study the chemical properties on the macroscopic scale for elements as massive as einsteinium. 4. As a result, chemical separations are generally very difficult to perform for identifying transactinides. 5. Several targets of californium isotopes were bombarded with beams of boron. Ex. 2 Make up questions to which the following sentences are the answers. 1. It will surely be possible to study the macroscopic properties of fermium. 2. The half-lives decrease into the millisecond and the microsecond range so that identification of the new nuclei becomes increasingly difficult. 3. Unlike neptunium and plutonium, these elements may undergo radioactive decay before being detected. 4. The identification of curium was possible because the alpha decay of the daughter nucleus, 238Pu, was already known and could be used as a signature for the identification of the curium precursor. 5. Elements 104 through 112 were discovered by observing the decay chain of their descendant nuclei. 6. The first identification of lawrencium was made at the Berkeley Lab’s Heavy Ion Linear Accelerator (HILAC) in 1961. 7. When a nucleus captures a neutron, it often tries to correct for its neutron excess by beta decay, turning a neutron into a proton and thus creating an atom with atomic number Z increased by one unit. 8. The rates for producing these elements in accelerator bombardments were incredibly low. Ex. 3. Identify the function of one and give Russian equivalents of the italicized words. 1. Reading books enlarges one's horizons. 2. It takes one much time and effort to carry out calculation of this kind. 3. Your definition is somewhat different from the one mentioned above. 4. The choice of the critical concentration is an arbitrary one. 5. One accepts standards which are specifically biological. 6. The technique does not allow one to isolate each individual component. 7. One cannot be surprised if one is not accustomed to the situation which is nullified by the surprise. Ex. 4. Recognize the words formed according to the following patterns and give their Russian equivalents. Pattern 1: N+-(u)al-> Adj. E x a m p 1 e: condition –  , conditional –  . Pattern 2: Adj. -ent/-ant -> N-ence/-ance Example: different –   ,   , difference –   ,  ,   . 48

A competent scientist – the competence of a scientist; a significant statement – the significance of a statement; an ignorantl audience – the ignorance of an audience; relevant information – the relevance of information. Pattern 3: Example: influence –   , to influence –    ; a question – , to question –    ,  . 1. Problems of this kind usually interest pure scientists. 2. Information theory aroused considerable interest among intellectualsJ 3. This fact limits the scope of investigation. 4. In the same wajj the necessary limits can be found for these coefficients. 5. We note that these figures are much more reliable than the previous ones.1 6. The text is difficult to read, there being too many reference note! in it. 7. This argument will convince anyone who doubts this point. 8. There can be no doubt about it. Ex. 5. Translate the following sentences paying attention to the inverted word order. 1. Best known and most important of all the oxides in the earth's crust is silicon dioxide, the chemical name for quartz and sand. 2. The North Pole region receives more solar heat j in the summer months than do the tropics, since the sun shines on it night and day. 3. We know that not only does the earth revolve around the sun, but the sun salso in motion. 4. Not until 1942 did scientists learn to make large quantities of any element out of an element composed of different atoms. 5. Darwin's ideas gave a new significance to the entire subject of paleontology. No longer were the ancient faunas and floras merely described and catalogued as interesting records of the past. The geologist now became interested in them not because they were old and dead but rather because they once were alive. 6, This explanation suggests that not until plant life flourished (evolved) did oxygen begin to accumulate in the earth's atmosphere. 7. Until about 25 years ago no data available on the small scale aspects of climate, nor had instruments been developed for measuring the several variables. 8. So far our study of minerals has been focused upon their chemical composition and physical properties. Were this all we wished to know, mineralogy and petrology would consist of little more than studies of chemistry and physics of earth materials. ORIGIN OF THE ELEMENTS Approximately 73% of the mass of the visible universe is in the form of hydrogen. Helium makes up about 25% of the mass, and everything else represents only 2%. While the abundance of these more massive (“heavy”, A > 4) elements seems quite low, it is important to remember that most of the atoms in our bodies and 49

Earth are a part of this small portion of the matter of the universe. The low-mass elements, hydrogen and helium, were produced in the hot, dense conditions of the birth of the universe itself. The birth, life, and death of a star are described in terms of nuclear reactions. The chemical elements that make up the matter we observe throughout the universe were created in these reactions. Approximately 15 billion years ago the universe began as an extremely hot and dense region of radiant energy, the Big Bang. Immediately after its formation, it began to expand and cool. The radiant energy produced quark-antiquarks and electron-positrons, and other particle-antiparticle pairs. However, as the particles and antiparticles collided in the high energy gas, they would annihilate back into electromagnetic energy. As the universe expanded the average energy of the radiation became smaller. Particle creation and annihilation continued until the temperature cooled enough that pair creation became no longer energetically possible. One of the signatures of the Big Bang that persists today is the long-wavelength radiation that fills the universe. This is radiation left over from the original explosion. The present temperature of this “background” radiation is 2.7 K. (The temperature, T, of a gas or plasma and average particle kinetic energy, E, are related by the Boltzmann constant, k = 1.38 x 10-23 J/K, in the equation E = kT.) The figure shows the temperature at various stages in the time evolution of the universe from the quark-gluon plasma to the present time.

The evolution of the universe At first quarks and electrons had only a fleeting existence as a plasma because the annihilation removed them as fast as they were created. As the universe cooled, the quarks condensed into nucleons. This process was similar to the way steam condenses to liquid droplets as water vapor cools. Further expansion and cooling allowed the neutrons and some of the protons to fuse to helium nuclei. The 73% hydrogen and 25% helium abundances that exists throughout the universe today comes from that condensation period during the first three minutes. The 2% of nuclei more massive than helium present in the universe today were created later in stars. 50

Substantial quantities of nuclei more massive than 4He were not made in the Big Bang because the densities and energies of the particles were not great enough to initiate further nuclear reactions. It took hundreds of thousands of years of further cooling until the average energies of nuclei and electrons were low enough to form stable hydrogen and helium atoms. After about a billion years, clouds of cold atomic hydrogen and helium gas began to be drawn together under the influence of their mutual gravitational forces. The clouds warmed as they contracted to higher densities. When the temperature of the hydrogen gas reached a few million kelvins, nuclear reactions began in the cores of these protostars. Now more massive elements began to be formed in the cores of the very massive stars. UNIT 9 Vocabulary list intercept1.1),Syn:interception2))    ,  # )  $ (  ..) 3)  missing 1. %#, %#, $ there is a page missing –     missing link – %#  long-range action   set of first species – !   species of type one –    species of zero type –    two angles of the same species –   ,      fusion 1) )  ;    ) ,    nuclear fusion –  /     fusion reaction –    Syn: melting , founding )    ,   dwarf 1. 1) )   )  ,  2)   !,    2.  , %;   , dwarf star   singularity 1)  2)   3)  4)   5)  6)  7)  8)   9)  sequence 1) )    ;   sequence of moves –  51

  ! - in sequence Syn: progression, series, succession )  ,   (  ) in chronological sequence –      collapse 1. 1)     , +, !;  ;  . He sank upon the ground in a collapse of misery. –      %,   . 2)  , $ the cutting of many tent ropes, the collapse of the canvas –  , !%#     ,   $  Syn: destruction , demolition 3) $, ;  filled with shame at the collapse of the enterprise –           rebound 1)  2)  3)  4)  THE SUN The Sun produces 4 x 1026 joules per second of electromagnetic radiation, a fraction of which is intercepted by Earth. The source of this energy is a series of reactions that converts four protons into one helium nucleus plus 26.7 MeV of energy that appears as energy in the reaction products. These fusion reactions occur only at the center of the Sun where the high temperature (~107 K) gives the hydrogen and helium isotopes enough kinetic energy to overcome the long-range repulsive Coulomb force and come within the short-range of the attractive strong nuclear force. The reaction energy slowly percolates to the surface of the Sun where it is radiated mainly in the visible region of the electromagnetic spectrum. Only the neutrinos escape from the Sun without giving up their energy. A detailed mathematical model of the temperature and density profile of the Sun powered by nuclear reactions also serves as a model of other stars. Since we cannot observe the nuclear reactions directly for confirmation of the nuclear processes, astrophysicists look to the neutrinos produced in the fusion of two protons to The solar energy reactions emit photons form deuterium and in the less common and neutrinos (14%) branch of the reaction chain where the fusion of 3He with 4He leads to isotopes of beryllium and boron that emit neutrinos. Massive underground neutrino detectors have found fewer neutrinos than expected from the model calculations. One speculation on the missing 52

neutrinos is that they convert from neutrinos associated with electron processes to those associated with muon or tau processes as they transit from the interior of the Sun to the Earth. Such a conversion can only occur if at least one of the neutrino species has a non-zero mass. This is a topic of much current research interest. EXERCISES Ex. 1. Make the following sentences negative. 1. This is a topic of much current research interest. 2. More massive cores continue to contract due to the intense gravitational force. 3. Underground neutrino detectors saw the neutrinos emitted during the few seconds of the collapse and the birth of either a neutron star or a black hole. 4. Massive underground neutrino detectors have found fewer neutrinos than expected from the model calculations. 5. This explosive expansion is called a supernova, one of the most spectacular events in astronomy. Ex. 2. Make up questions to which the following sentences are the answers. 1. Higher mass stars have internal temperatures (108 K) that allow the fusion of carbon with helium to produce oxygen nuclei and excess energy. 2. Massive underground neutrino detectors have found fewer neutrinos than expected from the model calculations. 3. Stars in this stage of evolution are known as red giants. 4. Once the core of the star is converted into iron-region nuclei, the star has nearly reached the end of its life. 5. This process turns the core of the star into neutrons and produces a huge burst of neutrinos. Ex. 3. Identify the function of this (these) and give Russian equivalents of the italicized words. 1. These outstanding discoveries were made by Russian scientists at the beginning of this century. 2. Usually a second alloy-layer appears between the outer coating and the base metal, and it is probable that this consists of different compounds. 3. Two basic schemes of replica are possible, these are illustrated in Fig. 1. 4. The definition does not make any mention of the rates of adsorption. These may be quite different for different materials. 5. I do not remember who was the first at this laboratory to use this term. Ex. 4. Recognize the words formed according to the following patterns and give their Russian equivalents. Pattern 1: V+-er/-or = N Example: to work – , worker –  ,  ; to transform –   , transformer –  . 53

1. Theory is an intellectual instrument granting a deep content to its designer and to its users. 2. The founders of the Royal society were typical natural philosophers. 3. The isolated inventor kills the usual source of innovation. 4. Some experimentors were prevented from doing experiments by their faith in a fallacious theory. 5. The lecturer should not try to surprise his listeners. Pattern 2: V+-ment = N Example: to develop –  , development –   , (),  ,   (). The announcement of discovery; the development of the national economy; recent developments in nuclear physics; the achievement of the solution; the achievements in space research; the establishment of a new principle; educational establishments of the country; a clear statement of the hypothesis. Ex. 5. Fill in the blanks with the appropriate words from the list given below. 1.An … is a body of land entirely surrounded by water. 2. Substances such as rocks and iron have strengths of the order of 10 dyn cm-2 and the … within the earth rises to this value at a depth of only about four km. 3. Diamond is pure crystalline carbon. Each carbon atom is … by four others at equal distances. 4. If primary cosmic … reached the earth, their effect would be lethal. 5. Scientists observe changes of …. on Mars and alternate days and nights. 6. All matter is known … of tiny particles, called molecules. 7. A … is the smallest part of any substance that still has the properties and the make up of that substance. 8. All molecules of any pure substance …. 9. The difference in properties of different substances is due to the fact that molecules that make them up …. 10. If the average kinetic energy exceeds the binding energy, the crystal structure breaks up and matter changes either into … or directly into a gas. 1) rays, 2) to be composed, 3) a liquid, 4) island, 5) seasons, 6) are different, 7) molecule, 8) are identical, 9) surrounded, 10) pressure OTHER STARS A star the size of the Sun will burn hydrogen into helium until the hydrogen in the core is exhausted. At this point, the core of the star contracts and heats up until the fusion of three 4He nuclei into 12C can begin. Stars in this stage of evolution are known as red giants. Low mass stars such as our Sun will then evolve into a compact object called a white dwarf. All nuclear reactions in a white dwarf have stopped. Higher mass stars have internal temperatures (108 K) that allow the fusion of carbon with helium to produce oxygen nuclei and excess energy. For 54

very massive stars, the exothermic fusion of low-mass nuclei into successively more massive nuclei can proceed all the way up to nuclei in the iron region (A ~ 60). The Table shows the temperature (1 keV is equivalent to 1.16x107 K), interior density and process lifetime that occur in stellar evolution of a star 25 times more massive than that of the Sun. Note the accelerating time-scale as higher mass nuclei are burned. Once the core of the star is converted into iron-region nuclei, the star has nearly reached the end of its life. Because the average binding energy per nucleon reaches a maximum at this point, there are no further energy-generating reactions possible and the star collapses because the gravitational force cannot be counterbalanced by the high-temperature and high-pressure interior. As the collapse of the core occurs, the density grows to the point where it becomes energetically favorable for electrons to be captured by protons via the weak interaction, producing neutrons and neutrinos. This process turns the core of the star into neutrons and produces a huge burst of neutrinos. When the collapse reaches nuclear density, the star rebounds explosively, throwing off much of its mass consisting of elements up to iron. This explosive expansion is called a supernova, one of the most spectacular events in astronomy. If the mass of the remnant core is less than two to three times the mass of the Sun, the core will settle down as a compact neutron star with no further nuclear reactions. More massive cores continue to contract due to the intense gravitational force until the size of the core diminishes to a point, a singularity called a black hole. The object is black because the gravitational force is so strong that nothing, not even light can escape. Table

The major stages in the evolution of a massive star Burning Stage

Temperature

Density

(keV)

(kg/m3)

Hydrogen

5

5x106

7x106 yr

Helium

20

7x108

5x105 yr

Carbon

80

2x1011

600 yr

Neon Oxygen Silicon

150 200 350

4x10 10

12

13

Time-scale

1 yr 6 months

3x10

13

1 day

15

seconds

Collapse

600

3x10

Bounce

3000

1017

milliseconds

Explosive

100-600

varies

0.1-10 seconds 55

In February of 1987 a supernova in a nearby galaxy was observed in the Southern sky. Underground neutrino detectors saw the neutrinos emitted during the few seconds of the collapse and the birth of either a neutron star or a black hole. The supernova continued to glow for months in the night sky due to the decay of radioactive isotopes that were produced in the explosion. Neutron-capture reactions on iron-region nuclei during the few moments of the explosion produced nuclei more massive than A = 60. A sequence of such reactions can produce elements all the way up to uranium, A=238. UNIT 10 Vocabulary list in contrast to     In contrast to their neighbors, they live modestly. – "     ,  ! . in contrast with   ! -   %  -  contrast  ;   the contrast between the two forms of government –   !     the contrast between town and country –   !    3)  ;  ,  in contrast with smth. –   ! - ;  %  - . Syn: comparison , confrontation to experience  ,    2)  ,  , ! We had never experienced this kind of holiday before and had no idea what to expect. – 9            ,   ! . Syn: undergo universal   ( #     ,     ..) 56

almost universal function –      almost universal relation –    $ momentum   ! ;  ,   (!#  );  + 2)  ,  ; !#   to gain, gather momentum –  !#%   angular momentum operator –     ! angular momentum vector –     ! towards ,   %  towards the south –  % 2) ,  $% , 3)      ;  , 

READ THE TEXT GALILEAN PHYSICS IN SIX INTERESTING STATEMENTS The study of everyday motion, Galilean physics, is already worthwhile in itself: we will uncover many results that are in contrast with our usual experience. For example, if we recall our own past, we all have experienced how important, delightful or unwelcome surprises can be. Nevertheless, the study of everyday motion shows that there are no surprises in nature. Motion, and thus the world, is predictable or deterministic. The main surprise is thus that there are no surprises in nature. In fact, we will uncover six aspects of the predictability of everyday motion: 1. We know that eyes, cameras and measurement apparatus have a finite resolution. All have a smallest distance they can observe. We know that clocks have a smallest time they can measure. Nevertheless, in everyday life all movements, their states, as well as space and time, are continuous. 2. We all observe that people, music and many other things in motion stop moving after a while. The study of motion yields the opposite result: motion never stops. In fact, several aspects of motion do not change, but are conserved: energy with mass, momentum and angular momentum are conserved in all examples of motion. No exception to conservation has ever been found. In addition, we will discover that conservation implies that motion and its properties are the same at all places and all times: motion is universal. 3. We all know that motion differs from rest. Nevertheless, careful study shows that there is no intrinsic difference between the two. Motion and rest depend on the observer. Motion is relative. This is the first step towards understanding the theory of relativity. 57

4. We all observe that many processes happen only in one direction. For example, spilled milk never returns into the container by itself. Nevertheless, the study of motion will show us that all everyday motion is reversible. Physicists call this the invariance of everyday motion under motion reversal (or, sloppily, under time reversal). 5. Most of us find scissors difficult to handle with the left hand, have difficulties to write with the other hand, and have grown with a heart on the left side. Nevertheless, our exploration will show that everyday motion is mirror-invariant or parity-invariant. Mirror processes are always possible in everyday life. 6. We all are astonished by the many observations that the world offers: colors, shapes, sounds, growth, disasters, happiness, friendship, love. The variation, beauty and complexity of nature are amazing. But despite all appearance, all motion is simple. Our study will uncover that all observations can be summarized in a simple way: all motion happens in a way that minimizes change. Change can be measured, and nature keeps it to a minimum. Situations – or states, as physicists like to say – evolve by minimizing change. These six aspects are essential in understanding motion in sport, in music, in animals, in machines and among the stars. This first volume of our adventure will be an exploration of such movements. In particular, we will confirm the mentioned six key properties of everyday motion: continuity, conservation, reversibility, mirror-invariance, relativity and minimization. Latin Words (/     !  ) Index – indices Criterion – criteria Appendix – appendices Phenomenon – phenomena

momentum - momenta basis - bases analysis - analysis datum –data EXERCISES

Ex. 1. Make the following sentences negative. 1. This first volume of our adventure will be an exploration of such movements. 2. Quantum theory predicts that clocks have essential limitations, and that perfect clocks do not exist. 3. Motion, and thus the world, is predictable or detereministic. 4. Quantum theory thus predicts tachyons, at least at very short time intervals. 5. For the same reason, motion backwards in time is possible over microscopic times and distances. 58

Ex. 2. Make up questions to which the following sentences are the answers. 1. Our study will uncover that all observations can be summarized in a simple way. 2. The variation, beauty and complexity of nature are amazing. 3. Space and time are tools of description that allow us to talk about relations between objects. 4. If humans were not macroscopic, they could neither observe nor study motion. 5. The classical idea of an empty vacuum is correct only when the vacuum is observed over a long time. Ex. 3. Find English equivalents in the text: 1.