(a)[1]
State the meaning of a photon.
(b(i))[2]
Indium-123 ($^{123}_{49}\text{In}$) is radioactive. A nucleus of indium-123 emits a $\gamma$-ray photon with energy $1.1\,\text{MeV}$. Determine the frequency of this $\gamma$-radiation.
(b(ii))[2]
Determine the photon's momentum.
(c)[2]
Before the $\gamma$-ray photon is emitted, the indium-123 nucleus is at rest. Use your answer in (b)(ii) to estimate the nucleus’s recoil speed after the photon has been emitted.