Special relativity

Let a particle of charge e and rest mass m, initially at rest in the laboratory, scatter
a photon of initial frequency νi. This is called Compton scattering. Suppose the scattered photon comes off at an angle θ from the incident direction. Use conservation of
four-momentum to deduce that the photon’s final frequency νf is given by
55 2.9 Exe rcises
1
νf
= 1
νi
+ h
�1 − cos θ
m
�