Учебное пособие Издание второе, переработанное и дополненное Москва Астрель • act 2005 удк 811. 111 (075. 8) Ббк 81. 2 Англ-923 К48 Компьютерный дизайн обложки студии «Дикобраз»

2. that
so that
in order that
lest чтобы не

Keep the temperature so that the Поддерживайте необходимую substance (should) not be cooled. температуру, чтобы вещество не

остыло.

3. though J _{хотякакбыни}
although J

Though he may (might) be busy he Как бы он ни был занят, он за-will complete the work on time. кончит работу вовремя.
Sentences to be translated.

1. 
   Acid is added so that the metal should dissolve.
   
2. 
   This gas must be kept in a special vessel lest it be evaporated.
   
3. 
   Though such an apparatus be developed, this would not solve the problem.
   

1. 
   One cannot speak of particles and waves as though they were two different things.
   
2. 
   Make exact calculations lest you should fail with your experiment.
   
3. 
   Be careful lest you should make mistakes in calculations.
   
4. 
   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.

• 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.