State what is meant by a photon.
A stationary cobalt-60 (
) nucleus emits a 
-ray photon of energy 
.
Calculate the wavelength of the photon.
Show that the momentum of the photon is 
.
Use information in (b)(ii) to determine the recoil speed of the cobalt-60 nucleus when the -ray photon is emitted.
that is directly proportional to its frequency 
, the energy is given by the equation:
is Planck’s constant.
.
.
