[سبحان من خلق الماء والسما]

Gama ray emits photons . Each photon has enery E=hv ,the photon mass is zero. with external factors, photon energy becomes less. by enisten facmous equation E=mc2 . the lost energy becomes mass until hv is zero and E=2mc2=hv . mc2 for the electron and mc2 for the postron . if they combine again with each other they will become photon and vice versa..