PX262 - A2 - compton scattering

in experiments with higher energy photons (x-rays), the photons scatter on electrons
if light is treated as a particle, the change in energy and the wavelength of the photon can be worked out using energy-momentum conservation

λ^{'} - λ = \frac{2 π ℏ}{m_{e} c} (1 - \cos θ)

where, $θ$ is the scattering angle of the photon, and $m_{e}$ is the mass of an electron