Question

Explain why the annihilation of an electron and positron creates a pair of photons rather than a
single photon.

Answer 1

Answer:

It cannot decay into a photon plus a recoiling electron because the latter alone would require an energy greater than mc2. But the final momentum cannot be zero, since photons always travel at the speed of light; an electron-positron pair can annihilate to make two photons, but not one.