Compton scattering deals with the collision of subatomic particles (electrons, protons, etc.) and photons (also known as electromagnetic energy packets). Usually the photons are in the X-ray range and the collision particle is assumed to be free and stationary relative to the photon. The wavelength of the photon usually increases after scattering, which means that its energy is lowered. This energy is transferred to the particle, which moves off in a random direction. This phenomenon conserves energy and linear momentum, and is regarded as the most convincing available evidence for the particle nature of electromagnetic radiation.