6. Be careful lest you should make mistakes in calculations.
7. In determining the orbit of a planet we may neglect accelerations ofthe sun and treat it as if it were at rest.
WORD AND PHRASE STUDY
A + | -iy = | Adv |
accurate + | -iy = | accurately |
• Form adverbs from the following adjectives and translate them into. Russian.
pure, comparative, rapid, equal, ordinary, certain, accidental, radioactive, previous, rare, heavy, presumble
READING (9A)
• Read the passage attentively and be prepared to describe the phenomenon of natural radioactivity.
THE DISCOVERY OF RADIOACTIVITY
As is the case with so many other discoveries, the discovery ofthe phenomenon of radioactivity was purely accidental. It was discovered in 1896 by a French physicist, A.H. Becquerel (1852—1908), who was interested at that time in the phenomenon of fluorescence, i.e. the ability of certain substances to transform the ultraviolet radiation that falls on them into visible light. In one of the drawers of his desk Becquerel kept a collection of various minerals that he was going to use for his studies, but because of other pressing matters, the collection remained untouched fora considerable period of time. It happened that in the drawerthere were also several unopened boxes of photographic plates, and one day Becquerel took one of the boxes in order to photograph something or other. When he developed the plates he was disappointed to find that they were badly fogged, as if previously exposed to light. A check on other boxes showed that they were in the same poor condition, which was difficult to understand since all the boxes were sealed and the plates inside were wrapped in thick black paper. What could be the cause of this mishap? Could it have something to do with one ofthe minerals in the drawer? Being of an inquisitive mind, Becquerel investigated the situation and was able to trace the guilt to a piece of uranium ore labeled "Pitchblende from Bohemia". The reader must take into account, of course, that at that time the name "uranium" was not in vogue as it is today, and that, in fact, only very few people, even among scientists, had ever heard about that comparatively rare and not very useful chemical element. But the ability of a uranium compound to fog photographic plates through a thick cardboard box and a layer of black paper rapidly brought this obscure clement to a prominent position in physics.
The existence of penetrating radiation that could pass through layers of ordinarily opaque materials as if they were made of clear glass was a recognized fact at the time of Becquerel's discovery. In fact, only a year earlier (1895) a German physicist, Wilhclm Roentgen (1845—1923), discovered what arc now known as X-rays, which can penetrate equally well through cardboard, black paper, or the human body.
Although special high voltage equipment is required to produce X-rays, the radiation "discovered by Becqucrel was flowing quite steadily and without any external excitation from the piece of uranium ore resting in his desk. What could be the origin of this unusual radiation? Why was it specifically associated with the clement uranium and, as studies found, with two other heavy elements known as thorium and actinium? The early studies of the newly discovered phenomenon, which was called "radioactivity", showed that the emission of mysterious radiation was completely unaffected by physical or chemical conditions. We can stick a radioactive element into a very hot flame or drop it into liquid air without the slightest effect on the intensity ofthe mysterious radiation it emits. No matter whether we have pure metallic uranium, or its oxide which is contained in pitchblende, the radiation flows out at a rate proportional to the amount of uranium in the sample. These facts ruled out any possibility of ascribing the phenomenon of radioactivity to any kind of chemical properties of this element, and led the early investigators to the conclusion that the phenomenon of radioactivity is the intrinsic property of the atoms of these peculiar elements and that its cause must be deeply rooted in the atomic interior.
• Find equivalents for the following Russian phrases.
как это происходит со многими другими открытиями; чисто случайное; интересоваться; видимый свет; из-за других неотложныхдел; в течение значительного периода времени; проявить пластины; были в таком же плохом состоянии; причина этой неудачи; могло ли это быть связано с; быть популярным; проникающая радиация; светонепроницаемые материалы; на излучение совершенно не влияет; без малейшего влияния; эти факты исключали возможность; причина, должно быть, кроется; внутреннее строение атома.
Re-read the passage and answer the following questions.
1. Who was the phenomenon of natural radioactivity discovered by?
2. Was this discovery really made quite accidentally?
3. What problem did Becquerel study at the time?
4. What did he keep minerals for in one ofthe drawers of his desk?
5. What did he see when he developed the photographic plates?
6. Why did he begin checking all the boxes with the plates?
7. Under what conditions were the boxes kept?
8. What was the cause of this mishap?
9. Was Becquerel greatly surprized to discover the radiation?
10. What penetrating radiation was discovered a year before that?
11. Who discovered this radiation?
12. Who were the first investigators ofthe phenomenon of radioactivity discovered by Becquerel?
13. What conclusion did the first investigators come to? Why did they come to such a conclusion?
14. What substances is the radiation emitted from?
Be prepared to say a few words about.
1. The history ofthe discovery of natural radioactivity.
2. Radioactive elements and types of radioactive emissions.
3. Radioactive processes in nature.
4. Radioactive emissions and their applications (radioisotopes, radiobiology, radiocarbon dating, radiodiagnosis).
Match each word in Column I with its synonym in Column II.
to be the case, because of, since, to take into account, no matter, to affect, to cause, to be in vogue, to rule out
II
to exclude, regardless of, to influence, because, to happen, to be in fashion, on account of, to take into consideration, to bring about
• Fill in the blanks with the proper word using the words in brackets.
(purified, purely, purification)
1. The process of... is rather complicated.
It is a... theoretical problem.
How is the material... in this case?
The discovery ofthe phenomenon of radioactivity was... accidental. (excited, excitation)
2. The radiation discovered by Becquerel was flowing without any external
... from the piece of uranium ore.
The highly... atoms arc often called Rydbergatoms, aftcrthe Swedish spectroscopist Yohanncs Rydberg.
Both the ion and target atom undergo electronic... during the collision. (exposed, exposure)
3. The technique is based on the use of long... to record an object's motion.
The plates were badly fogged, as if previously... to light.
Several ofthe animals which were... to radiation have died since.
CLASSWORK
READING (9B)
• Skim the passage rapidly (2 min.) and answer the following questions.
1. Did Becquerel observe in the experiment exactly what he expected to see?
2. What three rays did the original beam split into?
3. What were these rays called?
In order to study the nature of the discovered radiation, Becquerel arranged the following very simple experiment. He placed a small amount of uranium in a deep hole made in a lead block so that only a thin beam of radiation emerged from the groove. He also placed a magnet over the block in such a way that the magnetic lines of force were running perpendicular to the direction of the emerging beam. Under these conditions one could expect three different results.
If the radiation emitted by uranium were short electromagnetic waves similar to X-rays, no deflection should take place.
If, on the otherhand, the radiation were fast-moving electric particles, like the cathode and anode rays in J J. Thomson's tube, the beam should be deflected to the left in the case of a negative charge and to the right in the ease of a positive one. In Becquerel's experiment all three things happened, and the original beam emerging from the hole split into three parts. The part that consisted of particles carrying a positive charge was named ос-rays and was later proved (by Rutherford) to be a stream of doubly ionized helium atoms, i.e. a stream of helium nuclei. The part consisting of negatively charged particles, which turned out to be ordinary electrons, was named fj-rays, whereas the undeflected beam formed by short-wave electromagnetic radiation similar to X-rays received the name of y-rays.
• Re-read the passage and say a few words about the three kinds of radioactive rays. Give a headline to the text.
• Give a free translation of the following passage.
До открытия природной радиоактивности в конце XIX в. ядерные процессы оставались неизвестными.
Испускание излучения ураном, открытое в 1896 г. А. Беккерелем, было первым явлением ядерного происхождения, наблюдаемым человеком. В то время были только что открыты В. Рентгеном Х-лучи, создаваемые катодными лучами втрубках, в которых наблюдаласьтакже сильная флуоресценция. А. Пуанкаре выдвинул гипотезу, что испускание X-лучей может быть связано с явлением флуоресценции. А. Беккерель, желая проверить это предположение, использовал в качестве флуоресцирующих веществ соли урана, применявшиеся в работах его отцом. Он обнаружил, что соли действительно испускают излучение, способное производить фотографическое действие через л исток бумаги и ионизировать воздух подобно рентгеновским лучам, однако испускание этого излучения наблюдается также хорошо и с нефлуоресцирующими соединениями урана. Мари Кюри предприняла изучение этого нового явления в декабре 1897: она произвела ионизационным методом точное измерение интенсивности излучения урана и показала, что аналогичное излучение испускается торием.
HOMEWORK
(to be done in writing)
1. Translate into Russian.
1. It is necessary that the intensity of radiation should be measured very accurately.
2. The object behaves as if it were given some energy at the start.
3. Keep the temperature lest the substance should be overcooled.
4. In some calculations the air is treated as if it had no viscosity.
5. He suggested that the tunnel diode devices should be constructed from heavily doped semiconductors.
6. The whole weight of a body acts as though it were concentrated at a single point, this point being called the centre of gravity.
7. It is desirable that the errorsignal should be isolated from the detector.
8. The laws of mechanics require that the distance of each body from the center of gravity should be related to its mass.
2. Translate into English.
1. Предлагается, чтобы эксперименты провели в совершенно иных условиях.
2. Как бы мне хотелось принять участие в этой конференции!
3. Будь осторожен, чтобы прибор не сломался снова.
4. Проблемы обсуждалисьтак, какбудто имели большое значение.
5. Было бы трудно завершить исследование без его помоши.
6. Важно, чтобы реакция не прекратилась.
7. Он потребовал, чтобы все вычисления были проведены тщательно.
UNIT TEN GRAMMAR: GERUND
Forms of Gerund | Active | Passive |
Indefinite | solving | being solved |
Perfect | having solved | having been solved |
FUNCTIONS OF GERUND
WORD AND PHRASE STUDY
re- = again + re- + N = N re- + construction = reconstruction
re- + V = V re- + model = remodel
• Translate the following words into Russian:
retake, retrace, reestablish, rearrange, reproduction, redirect, redistribution, recharge, recapture, redefine
READING (10A)
• Read the passage attentively and be prepared to say a few words about "induced" or "artificial" radioactivity.
NUCLEAR FISSION
Following the discovery of neutrons in 1932 due to the English physicist James Chadwick many new types of artificial nuclear transformations have been investigated. Neutrons are the ideal projectiles for nuclear bombardment because they have no electrical charge and thus suffer no repulsion in their approach to atomic nuclei.
In some cases the impact of a neutron may result in the ejection of a proton or an a-particle, as in the reactions:
7NM + 0n1->6C,4 + 1H' 7Nl4 + 0n'->5B"+2H4
In some cases the incident neutron can eject another neutron without being captured itself:
Cl4+ n'-^C" +2 n1
6 О О О
whereas in other cases the incident neutron can be captured by the nucleus with the release of excess energy in the form ofay-quantum. The latter process, known as the radiative capture of neutrons, is of particular importance for heavy nuclear targets, since in this case the ejection of protons and a-particles is strongly hindered by the "outgoing" potential barrier surrounding the nucleus. I fit were not for the radiative capture ofthe neutron no heavier isotope of the bombarded clement would be formed. Sometimes these isotopes are stable so that no further nuclear transformation takes place:
r|6+ п'-^я017 + у
Hon 1
whereas in some other cases the radiative capture of a neutron leads to a (i-emission:
47Ag'w + on'->47Ag"u + Y 47Ag4°->48Cd» + e-
which is necessary to re-establish the proper neutron-to-proton ratio.
In the year 1939, a German radio-chemist, Otto Hahn, with his coworker, Frits Strassman, studied the effect of the neutron bombardment of uranium atoms, expecting to observe the formation of uranium isotopes with atomic weights higher than that of ordinary uranium, i.e., 238. To his great surprise Hahn found that the sample of uranium bombarded by neutrons contained radioactive atoms of a much lighter clement, barium. The mystery of this discovery was soon cleared up by two German physicists, Lisc Meitner and Otto Frisch, who suggested that in Hahn and Strassman's experiments the nuclei of U218 were split by incident neutrons into two nearly equal parts:
П238 + ni_4 Ba144+, ftKr94
32 о 56 36
Since the barium and krypton atoms produced in this process possessed excess neutrons, as compared with ordinary stable atoms of the same atomic weight (60Nd144 and 40Zr94), these so-called fission products emitted negative electrons, makingthem strongly radioactive. Frishand Meitner's interpretation of Hahn and Strassman's experimental finding as the splitting ofthe uranium nucleus into two nearly equal parts opened new vistas in the field of nuclear physics. Instead ofjust "chipping off' small pieces ofthe bombarded nucleus, as was the case in all previous experiments, here was a real breakup ofthe central body of the atom, the fission of a large droplet of the nuclearfluid into two half-size droplets. Instead ofjust the few million electron-volts of energy observed in previous experiments on artificial nucleartransformations, uranium fission liberates 200 MeV per atom.
The detailed theoretical studies ofthe process of nuclear fission were carried out by Niels Bohr and John Wheeler and published in the September 1939 issue of the Physical Review. This was the first and last comprehensive article on the theory of nuclear fission that appeared as "open literature" before the "security curtain" was drawn tight on that subject. According to Bohr and Wheeler, the fission of heavy nuclei resulting from the impact of a neutron is a resolution of a conflict between the opposing tendencies of nuclear (attractive) and Coulomb (repulsive) forces acting in the atomic nucleus.
• Find English equivalents for the following Russian phrases.
не испытывают никакой отталкивающей силы; на две почти равных части; вслед за открытием; загадка этого открытия была вскоре разрешена; как это происходило во всех предыдущих экспериментах; может привести к; идеальные частицы; радиационный захват; по сравнению с обычными устойчивыми атомами; испусканию протонов и альфа-частиц серьезно мешает; последний процесс особенно важен; эти так называемые продукты деления; никакого дальнейшего ядерного превращения не происходит; правильное отношение числа нейтронов к числу протонов; избыточные нейтроны; избыточная энергия; налетающий нейтрон
• Read the passage again and answer the following questions.
1. What problem is the text concerned with?
2. Who is the discovery of neutron due to?
3. Why are neutrons the ideal projectiles for nuclear bombardment?
4. What may the impact of a neutron result in?
5. What process is known as the radiative capture of neutrons?
6. Why is this process of particular importance for heavy nuclcartargcts?
7. What nuclear targets do you know?
8. What were the investigators looking for while experimenting with heavy nuclear targets?
9. What heavy nucleartargets did Otto Hahnand Fritz Strassman bombard with neutrons?
10. What did they expect to observe in the experiment?
11. What result did they really observe?
12. Could Otto Hahn and Fritz Strassman interpret the results of their experiment?
13. Who was the mystery of their discovery cleared up by?
14. What did Meitnerand Frisch suggest concerning Hahn's experiments?
15. What energy does uranium fission liberate in this artificial nuclear transformation?
16. Who carried out detailed theoretical studies ofthe process of artificial nuclear fission?
17. What is the fission of heavy nuclei according to Bohr and Wheeler?
• Be prepared to say a few words about:
1. Characteristics of neutron and its discovery.
2. Different types of artificial nuclear transformations.
• Choose the proper word to fill up the blanks in the sentences below.
(capture, incident, collisions, fission, releases, results in)
1. Particle... take place at locations known as integration regions.
2. This nuclear fission... large quantities of energy which finally takes the form of heat energy.
3. Neutron absorption frequently... the emission of secondary gamma rays.
4. In other cases the... neutron can be captured by the nucleus.
5. The spontaneous... of neutrons into positrons within 12 minutes through the emission of an electron is an evidence that neutrons can be considered as an electric modification of protons.
6. If it were not for the radiation... of the neutron no heavier isotope ofthe bombarded element would be formed.
• Translate into English making use of according to.
1. Согласно молекулярной теории, молекулы находятся в постоянном движении.
2. По утверждению автора, эта гипотезадовольно сомнительна.
3. Твердые тела классифицируются по их электрическим свойствам.
4. По словам докладчика, эти факты можно объяснить по-разному.
5. Что представляет собой деление тяжелых ядер, по утверждению Бора и Уилера?
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?
a) They do not carry enough energy.
b) They carry too high electric charges.
c) They carry no charge at all.
2. What process is responsible for nuclear energy liberation?
a) uranium fission.
b) a secondary process accompanying nuclear fission.
c) breakup of a uranium nucleus.
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.
• Read the passage again and translate the sentences marked with an asterisk.
• Give a free translation of the following text.
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
(to be done in writing)
1. Translate into Russian.
1. Providing such states existed, they could be produced by electron-positron collisions and could be detected by their characteristic decays.
2. Supposing an antinucleus were dressed with a cloud of positrons it would be an atom of antimatter.
3. In case a potential were applied to gas at low pressure, ionization ofthe molecules would result.
4. Should the neutron flux increase, the flow of coolant would increase too.
5. Had separate pieces of p- and n-type material been placed in contact, the p-n-junction would have been produced.
6. We would understand the operation of a transistor provided we became familiar with the mechanism of charge transitions across a junction formed between a piece of n-type semiconductor and a piece of p-type.
7. Should the reaction proceed smoothly, the end product might increase.
8. If it were not for the radiative capture ofthe neutron no heavier isotope ofthe bombarded element would be formed.
9. If the Moon were one half as massive as the Earth it would be two times as far from the center of gravity as the Earth is, if it were one third as massive as the Earth, it would be three times as far, and so on.
2. Translate into English.
1. Если бы мы проверили прибор, он бы не отказал.
2. Если бы не он, мы бы не обнаружили эту ошибку.
3. Если бы ее спросили об этом соединении, она не смогла бы рассказать о его свойствах.
4. Если бы они знали природу этого возбуждения, они получили бы другие результаты.
5. Если бы он был здесь, он бы сказал нам, куда поместить этот образец.
UNIT ELEVEN
GRAMMAR: GERUND
Forms of Gerund | Active | Passive |
Indefinite | solving | being solved |
Perfect | having solved | having been solved |
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 делил действие Х-лучей. of X-rays.
• Sentences to be translated.
1. His working at this problem was known to us.
2. Their having obtained new data is very important.
3. Our having been asked to make such an experiment surprised him.
4. I heard of his having carried out that research.
5. They spoke of the results having been achieved.
6. Einstein's being awarded the Nobel prize in physics soon became widely known.
WORD AND PHRASE STUDY
due to, thanks to, because of; on account of; owing to — вследствие,
благодаря, из-за
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 (11 A)
• 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".
Дата добавления: 2015-08-28; просмотров: 47 | Нарушение авторских прав
| <== предыдущая лекция | | | следующая лекция ==> |