Учебное пособие Издание второе, переработанное и дополненное Москва Астрель act 2005
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CLASS WORK READING (10В) • Skim the passage as fast as you can and choose the answer that suits the following questions best. 1. Why arc the two fragments ineffective in producing further fission processes?
2. What process is responsible for nuclear energy liberation?
FISSION NEUTRONS In spite of the fact that each of the two fragments produced in the fission of a uranium nucleus carries about 100 Mev of energy, these fragments are quite ineffective in producing further fission processes; this is due to the fact that the fission fragments carry a very high electric charge and are consequently strongly repelled by the other uranium nuclei with which they may collide. *Thus, the discovery of uranium fission would not contribute anything to the problem of the large-scale liberation of nuclear energy if it were not for a secondary process that was found to accompany nuclear fission. *It was discovered that apart from the two large fragments of the original nucleus, there are always several extra neutrons emitted in the breakup. In the case of U235 the average number of "fission neutrons" formed is 2.5 per uranium nucleus. *These fission neutrons formed in the breakup of one uranium nucleus may collide with the surrounding uranium nuclei and produce more fission and still more fission neutrons and if the conditions are favourable, the breeding (расширенное воспроизводство) of fission neutrons goes crescendo as does the breeding of pl248. Thus we get a branching chain reaction (разветвленная цепная реакция) and in practically no time all the nuclei of uranium in a given pile of this material break up with the liberation of a tremendous amount of energy.
В 1930 году немецкий физик Бете (Boethe) заметил, что бомбардировка бериллия природными сс-частицами из полония вызывала весьма специфическое излучение. Бете полагал, что это излучение было образовано у-квантами высоких энергий, и только через два года Чадвик (Chadwick) доказал, что это излучение было ни чем иным, как быстро движущимся пучком частиц, которые имеют ту же массу, что и протоны, но не несут электрического заряда. Эти новые частицы получили имя нейтроны. Нейтроны самопроизвольно (spontaneously) распадаются на протоны в течение 12 минут с испусканием электрона. Общее (collective) название для нейтронов и протонов — нуклон, нейтроны — нейтральные нуклоны, тогда как протоны — нуклоны, несущие положительный элементарный заряд. Не имея электрического заряда, нейтроны не подвержены (are not subjected to) действию электрических отталкивающих сил при приближении к ядру и могут легко проникать (penetrate) в заряженные ядра. Благодаря этому нейтроны являются идеальными бомбардирующими частицами. HOMEWORK (tobedoneinwriting) 1. Translate into Russian.
2. Translate into English.
UNIT ELEVEN GRAMMAR: GERUND
His knowing physics well To, что он знает физику хорошо, did not surprise us. нас не удивило. Everybody knows of Roentgen's Всем известно, что Рентген onpe-having determined the effect делилдействие Х-лучей. of X-rays. • Sentences to be translated.
WORD AND PHRASE STUDY due to, thanks to, because of; on account of; owing to — вследствие, благодаря, из-за 84 Copper has been used < due to thanksto because of on account of owing to > its great conductivity. V+-ment = N develop + -ment = development Form nouns from the following verbs and translate them into Russian. move, establish, agree, adjust, improve, excite, appoint V+ -ive = A act + -ive = active • Think of verbs corresponding to the following adjectives and translate them into Russian. creative, refractive, indicative, attractive, explosive, representative, expressive READING (11A) • Read the passage attentively and follow the first steps in the development of nuclear physics. Get ready to talk about the facts, hypotheses and experimental observations in the field. FROM THE HISTORY OF MESONS AND HYPERONS In the year 1932, a Japanese physicist, Hidekei Yukawa, suggested that the nuclear forces acting between protons and neutrons should be due to the presence of a new type of particle that serves as a "nuclear glue" holding the atomic nuclei together. According to Yukawa's theoretical consideration, the new particles must have a mass intermediate between that of protons and that of electrons, so they received the name mesons (from the Greek mesons meaning "between"). Five years after the introduction of these purely hypothetical particles for the explanation of nuclear forces, they were actually observed in cosmic rays by an American physicist, Carl Anderson. The so-called "primary cosmic rays" bombarding the atmosphere of our planet are formed by streams of extremely high-energy protons and a few other heavier positively charged nuclei that are probably accelerated by electromagnetic fields in interstellar space. The energies of these primary cosmic particles range from comparatively low values to thousands of billions of electron-volts. Colliding with the nuclei of atmospheric oxygen and nitrogen at the outer fringes of the atmosphere, these primary cosmic ray particles produce various kinds of penetrating radiations, including high-energy y-quanta and streams of negative and positive electrons; in fact, positive electrons were first discovered in cosmic rays. Observing the tracks formed by cosmic ray particles in a vertical cloud chamber placed between the poles of a strong magnet, Anderson noticed that the trajectories of some of the particles, both positively and negatively charged, were bent by a magnetic field more than would be expected in the case of fast protons but considerably less than should be the case with electrons. From the observed magnetic deflection, Anderson estimated that this new kind of particle is about 200 times heavier than an electron, in agreement with Yukawa's theoretical prediction. These particles were first called "heavy electrons", but the name was later changed to "mesons". Later studies have shown that there are actually two kinds of mesons, heavier ones called п-mesons or pions, and lighter ones known as u-mesons. Both pions and muons can carry either a positive or negative electric charge (п+, л-, u.+, u.), and in addition there also exist neutral pions (n°). All of these new particles, as well as the positive and negative cosmic ray electrons (e+, e) are genetically related to each other and form a sequence somewhat similar to the sequence of the radioactive elements. It is now established that the primary high-energy protons entering the outer fringes of the atmosphere give rise to neutral and charged pions. Neutral pions possess a very short lifetime (about 10"" sec) and, in spite of their high velocity, break up into two y-quanta: n°-* y + y1 before reaching the surface ofthe earth. The charged pions (both positive and negative) live somewhat longer (108 sec) but still most of them break up high in the atmosphere according to the equation: я*-* u* + neutrino Accordingly, for the study of pions and their decay into muons photographic equipment attached to large balloons must be sent high into the stratosphere. The mean lifetime of muons is comparatively long (106 sec), and many of them reach the surface of the earth and permit themselves to be photographed in ordinary cloud chambers. Since cloud chamber equipment is too bulky and heavy to be sent up in balloons, cosmic ray researchers have developed a new method for photographing the tracks of cosmic particles at high altitudes. Instead of using the ionizing properties of fast charged particles passing through humid air, the new method is based on the fact that these particles affect the grains through which they pass when they travel through a finegrained photographic emulsion. When the photographic plate is developed it shows dark streaks that correspond to the trajectories followed by particles. A very rare photograph of this kind showing the formation of a pion resulting from the collision of a primary cosmic ray particle with a composite nucleus and the subsequent decay of this pion into a muon and an electron is shown in the figure below.  Apart from mesons, which have a mass intermediate between those of an electron and a proton recent studies of cosmic rays have discovered particles that are heavier than protons and are known under the collective name hyperons. The study of these particles and of their interrelation with each other was, for a time, the most interesting and most important field of exploration in physics. • Find equivalents for the following phrases. ядерные силы, вероятно, обуславливаются наличием; в соответствии с теоретическими предположениями; протоны чрезвычайно высоких энергий; межзвездное пространство; энергии колеблются от сравнительно низких величин до; проникающее излучение; и положительно и отрицательно заряженные; приблизительно в 100 раз тяжелее; в соответствии с теоретическим предположением; либо положительный, либо отрицательный электрический заряд; кроме того, существуют нейтральные пионы; а также электроны; ряд, несколько похожий на; несмотря на их высокую скорость; среднее время жизни; слишком громоздкое; набольших высотах; вместо использования; воздействует на зерна; когда фотопластинку проявляют; помимо мезонов, соответствующих траекториям, по которым следуют частицы; пион, образующийся в результате столкновения • Re-read the passage and supply answers to the questions.
• Match the synonyms from both columns. II mean, altitude, to affect, to estimate, usual, to result in, regardless of, to range, actually, in addition, similar, to give rise to, in spite of, ordinary, to result from alike, to arise from, height, besides, in fact, average, to evaluate, to influence, to vary to cause, to result in, to give rise to, to bring about — привести к ... to be caused, to result from, to be due to, to arise from — являться результатом ... • Translate into Russian paying attention to the words in bold type.
Remember! определительное существительное (какой?) <— (какой?) «- (что?) сущ. + сущ. + сущ. При переводе такой группы слов следует прежде всего начинать перевод с последнего существительного (определяемого). Все остальные существительные, стоящие перед ним, его определяют. gam ma-ray sensitivity — чувствительность по гамма лучам energy-charge relation - зависимость заряда от энергии • Translate the following word combinations. electron rest-mass, phase shift analysis, electron velocity distribution, pulse series generator • Translate into English using both ... and, either... or, neither ... nor.
CLASSWORK READING (1 IB) • Skim the passage rapidly and explain (he title. THE MYSTERIOUS NEUTRINO The early studies of radioactive (3-decay (the emission of an electron by an unstable atomic nucleus) led to the conclusion that there is something wrong with the energy balance involved. While the (x-particles emitted by a given radioactive element always carry a well-defined amount of energy characteristic of that particular clement, (3-particles show a wide energy spread (разброс) ranging from almost zero to rather high energy values. Since the total energy liberation in the transformation of one atomic nucleus into another is expected to be the same for all nuclei of a given kind, it was suspected that there would be another particle coming out ofthe nucleus along with the electron that carries the missing (недостающий) balance of energy. This hypothetical particle, which must be electrically neutral and must have a mass that is much smaller than even the mass of an electron, received the name neutrino which means "little neutral" in Italian. The absence of electric charge and the extremely small mass allow neutrinos to penetrate thick material layers with the greatest of ease; a thick concrete (бетонная) wall is just as ineffective in stopping a beam of neutrinos as a chicken wire fence (проволочная изгородь) is in stopping a swarm (рой) of mosquitos. The neutrinos that are produced in great quantities near the center of the sun in the process of nuclear energy production pierce its entire body and fly away as if there were nothing there at all. It has been estimated theoretically that in order to stop effectively a beam of neutrinos we would need a shield several light-years thick. In spite of the almost incredible ability of neutrinos to make their "getaway" (выход) physicists managed in 1955 to stop a few of them, thus finding unquestionable proof of their existence. F. Reines and C. Cowen of the Los Alamos Scientific Laboratory used forthis purpose the collision process between neutrinos and the nuclei of hydrogen atoms (protons) in which the neutrino was expected to produce a positron and to transform the proton into a neutron: я + neutrino^ n + e+ These two scientists built a giant particle counter that registered neutrinos as well as positrons and placed it near one of the nuclear piles. The nuclear reactions taking place in the operating pile produce a tremendous number of neutrinos that stream out through a heavy shielding which holds back all other nuclear radiations. Although the chance of a neutrino hitting a proton and producing the above-mentioned reaction is only 1 out of 103u, some of these reactions do actually take place, resulting in the simultaneous appearance of a neutron and the accompanying positron. Thus, the uncatchable neutrino was finally caught and joined the company of well-established elementary particles. • Re-read the passage and give answers to the following questions.
• Give a free translation of the following passage. Интерес к космическим лучам сверхвысоких энергий объединяет представителей двух наук — астрофизики и физики элементарных частиц. Дело втом, что, с одной стороны, источниками этого излучения могут быть такие пока недостаточно познанные астрономические объекты, как пульсары, оболочки сверхновых звезд, черные дыры, активные ядра галактики и квазары, и потому информация, приносимая космическим излучением, очень важна для физики космоса. С другой стороны, это излучение состоит из частиц самых больших из известных нам энергий, в тысячи и миллионы раз превосходящих те, которые достигнуты на созданных человеком ускорителях. Вот почему изучение таких частиц имеет важнейшее значение и для физики высоких энергий. В целом же можно сказать, что исследование космических лучей — это своего рода глубокая разведка (reconnaissance) в «горячих точках» науки. HOMEWORK (to be done in writing) |