Changes

'''Annihilation''' is the process in which [[matter]] and [[antimatter]] interact converting all their [[Rest Mass|rest mass]] into [[energy]] resulting in a pair of two or more [[Gamma-ray|gamma ray]] [[photon]]s being emitted in opposite directions.

: *'''Annihilation''' occurs when [[particle]]s of [[matter]] and [[antimatter]] interact at extremely close range.: *During '''annihilation''' the total [[Rest Mass|rest mass]], as well as the [[Kinetic Energy|kinetic energy]], of the [[particle]]s is equal to the total [[energy]] of the two [[Gamma-ray|gamma ray]] [[photon]]s.: *In '''annihilation''' [[Conservation of Momentum|conservation of momentum]] is conserved due to the [[momentum]] of the two [[Gamma-ray|gamma ray]] [[photon]]s travelling in opposite directions.*For a-level physics you only need to consider the special case of 2 [[Gamma-ray|gamma ray]] [[photon]]s being [[emit]]ted.