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What are alpha rays ? Briefly explain alpha decay. |
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Answer» Alpha decay. Alpha decay is a process involving the emission of a fast-moving helium nucleus (an alpha-PARTICLE) by nuclei which generally contain 210 or more nucleons. Since `""_(2)H^(4)` contains two protons and two neutrons, after an alpha emission the PARENT nucleus is transformed into a daughter nucleus which has (i) an atomic number SMALLER by two and (ii) mass number smaller by four. Transformation of the `""_(z)X^(A)` nucleus into then `""_(z-2)X^(A-4)` nucleus by an alpha decay can be expressed by the equation. `""_(z)X^(A)=""_(z-2)Y^(A-4)+""_(2)HE^(4)+Q`. e.g. `""_(92)U^(238) rarr ""_(90)Th^(234)+""_(2)He^(4)+Q` If `m_(X), m_(Y)` and `m_(alpha)` represent the mass of parent nucleus X, daughter nucleus Y and `alpha` particle respectively , then the energy released Q is given by `Q=[m_(X)-(m_(Y)+m_(alpha))]c^(2)` The VALUE of K.E. of `alpha`-particle is of the order of 4.9 M eV for various `alpha`-emitters. |
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