Compton Scattering

Photon scatters off a free electron: Δλ = λ_c(1 − cosθ) — drag the angle slider

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Δλ (pm)
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E' scattered (keV)
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KE electron (keV)
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Electron angle φ (°)
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E'/E₀
Compton Formula: Δλ = λ' − λ = λ_c(1 − cosθ), where the Compton wavelength λ_c = h/(m_e c) = 2.426 pm. Scattered photon energy: E' = E₀ / (1 + (E₀/m_e c²)(1 − cosθ)). The electron recoils at angle φ where cotφ = (1 + E₀/m_e c²)·tan(θ/2). At θ=180° (backscatter), maximum energy is transferred. This 1923 experiment by Arthur Compton confirmed the particle nature of light, winning the 1927 Nobel Prize. Click anywhere on the canvas to change the scattering angle.