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A radioactive substance is placed in a lead block. The radiations coming out are subjected to an electrostatic field. One type of radiations move towards negative plate, a second type moves towards positive plate and the third remains unaffected. Similarly when the radiations are subjected to magnetic field in a direction perpendicular to their direction of motion alpha particles moves one side, beta particle moves to the other side and gamma rays remains unaffected. This clearly shows that there are three types of radioactive radiations 1) alpha, 2) beta and 3) gamma.
Properties:
1. Gamma rays are electromagnetic radiations like visible light or X-rays bur their wavelengths are smaller than that of X-rays.
2. Gamma rays are not deflected by electric or magnetic fields and hence they do not carry any charge.
3. They produce ionisation but the ionisation power is small.
4. Gamma rays are highly penetrating.They can pass through many centimeters length of lead.
5. Gamma affect photographic plates and cause fluorescence in various materials.
6. They travel with velocity of light.
7. Gamma rays are very harmful to human tissues.
8. Gamma rays produce photoelectric effect when they incident on solid surfaces.