Gamma Rays

Uranium- 238 decays to thorium- 234 with half-life 5xx10^(9) yr . The resulting nucleus is in the excited state and hence further emits gamma -rays to come to the ground state. It emits 20 gamma -rays per second. The emission rate will drop to 5 gamma -rays per second in

In gamma ray emission from a nucleus

In gamma ray emission from a nucleus

To produce an electron-position pair, the minimum energy of gamma -ray photon must be