Introduction to the World of Nuclear Physics. Lidiya Strautman

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СКАЧАТЬ 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. Трудно найти человека, который бы не задумывался над этим. 2. Это вопрос, который касается всех. 3. Трудно сказать, какая из этих проблем сложнее. 4. Необходимо решить, кто из них возглавит эту работу. 5. Трудно сказать, какие вопросы будут нас волновать через два десятка лет. 6. Никто не знает, кто первым применил это устройство. 7. Лектор сказал, какую литературу надо прочитать по этому предмету. 8. Трудно было решить, кто из них был прав.

      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 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 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 ускоритель протонов

      transform трансформировать; подвергать трансформации, преобразованию, б) преобразовывать один вид энергии в другой (напр., механическую энергию в электрическую)

      transformation 1) видоизменение 2) отображение 3) перегруппировка 4) превращение 5) преобразование

      emit 1) излучать, испускать, выделять (свет, тепло, запах и т. п.); выбрасывать, извергать (пепел, дым, лаву) the rays of heat that are emitted by the warm earth – теплые волны, испускаемые нагретой землей The factory has been emitting black smoke from its chimneys, which is against the law. Из труб завода до сих пор вырывается черный дым, это противозаконно.

      half-life 1) период полупревращения 2) период полураспада 3) полупериод распада

      half-life-decay полураспад, СКАЧАТЬ