**Compton Scattering** is the scattering of a high frequency photon after an interaction with a charged particle (usually an electron), decreasing the photon energy and transferring it to the recoiling electron. If the photon gains energy, it is known as [[Inverse-Compton Scattering]]. ![[scattering_compton.gif|align:center|500]] The energies of the photon and electron (which sum to a constant) can be expressed as a function of the photon scattering angle ($\theta$), from the initial photon direction. Plotting this function for the photon and electron show that there is essentially no energy transferred by photons that don't change direction ($\theta = 0$ or $\theta=2\pi$), but a large energy transfer for photons that are back scattered in the direction they came from. ![[scattering_compton_energy.png|align:center|400]]