Since the rest energy of an electron and its antiparticle a positron is 0.511 MeV,a gamma ray must have an energy larger than 1.022 MeV to produce an electron-positron pair.

Question

Quizplus · Accepted Answer

This statement is true according to the conservation of energy and momentum in particle interactions. The energy of a gamma ray photon must be greater than the combined rest mass energy of an electron and a positron to create them from the photon's energy. The total rest mass energy of an electron and a positron is 2 × 0.511 MeV = 1.022 MeV. Therefore, a gamma ray photon with energy less than 1.022 MeV cannot create an electron-positron pair.

Since the Rest Energy of an Electron and Its Antiparticle