When a positronium atom decays, it emits two photons. What are the energies of the photons?
A) 0.256 MeV and 0.256 MeV
B) 0.511 MeV and 1.022 MeV
C) 0.225 MeV and 0.285 MeV
D) 0.511 MeV and 0.511 MeV
E) 1.02 GeV and 938. MeV

Question

Quizplus · Accepted Answer

When a positronium (a bound state of an electron and its antiparticle, a positron) decays, it annihilates to produce two photons. The energy of each photon is equal to the rest mass energy of the electron (or positron), which is 0.511 MeV. Therefore, both photons will have an energy of 0.511 MeV each.

When a Positronium Atom Decays, It Emits Two Photons