Very high frequency (and therefore very high energy) electromagnetic radiation emitted as a consequence of radioactivity
Electromagnetic radiation emitted by radioactive decay and having energies in a range from ten thousand (10) electron volts. a beam of light with a short wavelength, that can pass through solid objects radi'ation. Penetrating very short-wavelength electromagnetic radiation, similar to an X ray but of higher energy, that is emitted spontaneously by some radioactive substances (see gamma decay, radioactivity). Gamma radiation also originates in the decay of certain subatomic particles, and in particle-antiparticle annihilation (See also antimatter). Gamma rays can initiate nuclear fission, can be absorbed by ejection of an electron (see photoelectric effect), and can be scattered by free electrons (see Compton effect)