An electron and a positron annihilate while both are initially at rest
PHYSICS · Single correct · A Level · Physics · Particles and radiation · Particles and radiation
Problem
An electron and a positron annihilate while both are initially at rest. Which one of the following best explains why two photons, and not one, are emitted?
(a) Emission of two photons conserves electric charge, which a single photon cannot do.
(b) Two photons are required because the total spin of the electron–positron system cannot be carried away by a single photon.
(c) Two photons are required to conserve both energy and linear momentum simultaneously.
(d) There is not enough energy available to create a single photon.