Penetrating energy/radiation

High-energy radiation may be classified into photon and particulate radiation. Gamma radiation is utilized for fundamental studies and for low-dose rate irradiations with deep penetration. Radioactive isotopes, particularly cobalt-60, produced by neutron irradiation of naturally occurring cobalt-59 in a nuclear reactor, and caesium-137, which is a fission product of uranium-235, are the main sources of gamma radiation. X-radiation, of lower energy, is produced by electron bombardment of suitable metal targets with electron beams, or in a... 

Beta particles were described by Rutherford as fast moving electrons. They are negatively charged with no protons or neutrons (or they have a mass of 0.) A beta particle is released when a neutron breaks into a proton and an electron. It is fast moving, high energy radiation and can penetrate paper and skin. A 3 mm thick sheet of metal is needed to stop it. 

X ray (p. 809) A form of high-energy, penetrating electromagnetic radiation emitted from some materials that are in an excited electron state. 

Gamma radiation is the most convenient type of high-energy radiation for initiating polymerization because its high penetrating power affords uniform irradiation of the system. Because gamma rays are absorbed to the same extent by solids as by liquids, solid monomers can be polymerized readily. This allows polymerization of many monomers at low temperatures. 

Another possibility of decomposing a C=C-double bond is supplying energy. Radiation contains energy in different forms the heat radiation of a heater or an electric light bulb is known as well as the radiation of an X-ray tube able to penetrate body tissue. Particularly suitable for curing, thus the polymerization of the C=C-monomers, is ultraviolet radiation (UV-radiation), known as a part of solar radiation. If these ultraviolet rays meet with the adhesive monomers to which so-called photoinitiators are added, the double bonds included in the monomers will be decomposed and polymerization proceeds in a way similar to that described in Section 4.3. 

A sunscreen is a chemical substance, which is applied to the skin to carry out the same function as melanin, namely to prevent high energy radiation from penetrating to the living cells in the lower layers of the skin. Sunscreens have to absorb in the proper region of the spectmm, and to be cosmetically acceptable they should be colorless,... 

ENERGY LOSS AND PENETRATION OF RADIATION THROUGH MATTER 123... 

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