Sunday, January 3, 2010

20-Nuclear Physics

Nuclear Physics (Atomic Structure and Radioactivity)

Mass Number/Nucleon Number - the number of nucleons (that is, protons and neutrons) found in the nucleus.

Atomic Number/Proton Number - the number of protons in the nucleus of an atom.

Isotope - one of two or more atoms of the same element that have the same number of protons in their nucleus but different numbers of neutrons.

Unified Atomic Mass Unit- the mass of one-twelfth of the mass of a carbon-12 atom.

Mass defect - the difference between the total rest mass of the nucleons in a nucleus in the unbounded state and the rest mass of the nucleus.

Binding Energy - the energy released when a nucleus is formed from its constituent protons and neutrons.

Binding Energy per nucleon – Binding energy is the energy released when a nucleus is formed from its constituent protons and neutrons. Binding energy per nucleon is binding energy divided by the number of nucleon in the nucleus.

Nuclear Fusion - the forming of a larger nucleus from two nuclei of low nucleon number, with the release of energy.

Nuclear Fission - the splitting of a nucleus of high nucleon number into two smaller nuclei of approximately equal mass with the release of energy and neutrons

Radioactivity - is the spontaneous nuclear disintegration in which an unstable nucleus with the emission of one or two of the different types of radiation namely alpha, beta and gamma.

– this describes the nature of radioactive decay (shown by the fluctuation of the decay readings for any given sample of a radioactive material, it is not possible to predict which nucleus will decay next and exact when it would decay.

(Note: Although the decays in a sample may be random, any nucleus has a constant probability of decay per unit time, referred to as the decay constant).

Spontaneous Decay - the emission is unaffected by environmental factors such as temperature and pressure.

Activity - the number of nuclear disintegrations per unit time. (Unit - Becquerel, Bq).

Count Rate - the measure of the rate of nuclear disintegration received by the detector, which may include the background count

Decay Constant - the probability of the decay of a radioactive nucleus per unit time.

Half-life - the average time taken for half of the remaining radioactive nuclei in a sample of the nuclide to decay.

Background Radiation – the radiation detected by a radiation counter when no radioactive source is nearby. This is mainly due to cosmic rays from space.


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