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Compton scattering
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<p>Compton scattering (or the Compton effect) is the <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum</a> theory of high frequency <a href="/facts/Photon/mFNhAEzA">photons</a> <a href="/facts/Scattering/nMou7lEH">scattering</a> following an interaction with a <a href="/facts/Charged_particle/2zqBJGse">charged particle</a>, usually an <a href="/facts/Electron/L0KBo5cW">electron</a>. Specifically, when the photon hits electrons, it releases loosely bound electrons from the outer <a href="/facts/Valence_electron/mXPA15VP">valence shells</a> of atoms or molecules. </p><p>The effect was discovered in 1923 by <a href="/facts/Arthur_Compton/FrNYLBj4">Arthur Holly Compton</a> while researching the scattering of <a href="/facts/X-ray/wseP79cN">X-rays</a> by light elements, and earned him the <a href="/facts/Nobel_Prize_in_Physics/o6w1nCbr">Nobel Prize in Physics</a> in 1927. The Compton effect significantly deviated from dominating classical theories, using both <a href="/facts/Special_relativity/vsFFc63E">special relativity</a> and <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum mechanics</a> to explain the interaction between high frequency photons and charged particles. </p><p>Photons can interact with matter at the atomic level (e.g. <a href="/facts/Photoelectric_effect/gIDcdm5U">photoelectric effect</a> and <a href="/facts/Rayleigh_scattering/o0MQtPMM">Rayleigh scattering</a>), at the nucleus, or with just an electron. <a href="/facts/Pair_production/MmN9EUG0">Pair production</a> and the Compton effect occur at the level of the electron. When a high frequency photon scatters due to an interaction with a charged particle, there is a decrease in the <a href="/facts/Energy/wd8PrQM7">energy</a> of the photon and thus, an increase in its <a href="/facts/Wavelength/kcJU0ymz">wavelength</a>. This tradeoff between wavelength and energy in response to the collision is the Compton effect. Because of <a href="/facts/Conservation_of_energy/12CdN4Ik">conservation of energy</a>, the lost energy from the photon is transferred to the recoiling particle (such an electron would be called a "Compton Recoil electron"). </p><p>This implies that if the recoiling particle initially carried more energy than the photon, the reverse would occur. This is known as inverse Compton scattering, in which the scattered photon increases in energy. </p>