Compton scattering

In physics, Compton scattering, or the Compton effect, is the name used for what happens to the energy (or frequency or wavelength) of an X-ray or gamma ray photon when it interacts with matter; the wavelength increases (or energy/frequency decreases) as it scatters off electrons. This scattering is one of the main things that happen when gamma rays meet matter. The Compton effect was studied by Arthur Holly Compton in 1923.

Compton Scattering Media

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  Fig. 2: A photon of wavelength \lambda comes in from the left, collides with a target at rest, and a new photon of wavelength \lambda' emerges at an angle \theta. The target recoils, carrying away an angle-dependent amount of the incident energy.

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  Fig. 3: Energies of a photon at 500 keV and an electron after Compton scattering.