Particles

Question 1

Annihilation

Answer 1

The conversion of the mass of a particle and it’s antiparticle to energy in the form of a pair of photons of EM radiation
(Two photons so momentum and energy are conserved)

Question 2

Pair production

Answer 2

Process where a photon of EM radiation ceases to exist creating a particle and it’s antiparticle pair in its place
(Another particle e.g. nucleus must be present to conserve energy and momentum)