HKNIC - Nuclear Radiation
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Nuclear Radiation
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In particle form, radiation is known as particle radiation. Energy from particle radiation gives speed to fast-moving sub-atomic particles. It commonly consists of three forms. Alpha radiation is the energy of moving helium nuclei and can be stopped by a sheet of paper or the outer surface of the skin. Beta radiation is the energy of moving electrons or positrons and can be stopped by a sheet of aluminium. Neutron radiation, the energy of moving neutrons, can be stopped only by a layer of dense material such as concrete. Most of these particles carry enough energy to ionise matter.
For radiation to be ionising, the particles need to have high energy and be in a position to affect an atom. Gamma rays are high energy photons that will interact with charged particles in the atom. Incoming charged particles such as alpha and beta particles will also interact with the electrons in the atom to produce ionisation. While neutrons themselves have no charge and do not interact with the electrons, they will interact with the protons, particularly in the case of hydrogen, to produce proton radiation which will then interact with electrons. Neutron interaction with an atomic nucleus may also make it radioactive, that is, produce ionising radiation.
All matter is made up of atoms. Most of the atoms that we encounter in our daily life are stable and will not change, but a large number do. The nuclides of many types of elements have atoms that are unstable and can change into atoms of different elements. The change takes place when an unstable atom releases its excess energy, in the form of a particle or an energy pulse, which we call radiation. Depending on the type of excess energy being released, the atom may become a different type of element and the process will continue until the atom has become stable. The radiation associated with the change in the atoms is called nuclear radiation.