LITMIR.BIZ

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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. Мне трудно об этом спорить. 2. Им важно подкрепить теорию дополни-тельными экспериментальными данными. 3. Физикам важно поддерживать контакт, с биологами. 4. Ребенку необходимо учиться на собственном опыте. 5. Нам часто трудо угадать, каким будет будущее. 6. Естественно, что на такой анализ затрачивается около года. 7. Необходимо, чтобы реакция была ускорена. 8. Чтобы две молекулы вступили в реакцию, они должны столкнуться.

      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 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 He 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 Po 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 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 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) короткоживущий 2) кратковременный 3) мимолетный 4) недолговечный 5) нестойкий

      short-lived isotope короткоживущий изотоп, short-lived radiation излучение короткоживущих изотопов

      fission 1. 1) деление, разделение на части, раскалывание – binary fission Syn: splitting 1. 2) расщепление, деление атомного ядра при цепной реакции -nuclear fission 3) деление ядра. 2. 1) разбиваться, раскалываться 2) а) расщепляться, делить (о делении ядра атома) б) вызывать расщепление, деление (ядра атома)

      approximately 1) аппрокcимативно 2) приблизительно 3) примерно

      approximately compact set – аппроксимативно компактное множество

      approximately continuous function – аппроксимативно непрерывная функция

      approximately differentiable function аппроксимативно дифференцируемая функция

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 (a), beta (p), and gamma (y) 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.

      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

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