 Arthur Holly Compton

Arthur Holly Compton explained the angle-dependent change of X-ray wavelength by treating a photon as carrying both energy and momentum. For scattering from an initially stationary free electron, conservation gives ${\lambda }^{\prime }-\lambda =h(1-\cos \theta )/(m_{e}c)$. The Compton scattering shift therefore depends on angle and the electron mass, rather than on the illuminating wavelength alone. Comparing the measured scattered lines with this relation tested the particle-like energy–momentum account of radiation.^[ref]

A physicist known for Compton scattering.

Nobel Prize biography: www.nobelprize.org/prizes/physics/1927/compton/biographical/