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Light-matter interactions

Light-matter interaction comprises interactions of photons (massless, uncharged wave packets, traveling at the speed of light) with electrons (mass-bearing, electrically charged particles, occupying atomic or molecular orbitals). Different effects happen at different photon energies, e.g.:

• at low energy (eV, visible light), the photoelectric effect emits electrons from a material;
• at medium energy (keV, X-rays), the Compton effect scatters photons with lowered energy off charged particles; and
• at high energy (MeV and higher, gamma rays), pair production converts photons near atomic nuclei into electron-positron pairs.

Other effects caused by photon-electron interaction include fluorescence, phosphorescence, Rayleigh scattering, and Cherenkov radiation.

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