Compton Scattering Calculator

About this calculator

This calculator finds the Compton wavelength shift of a photon scattered off a stationary electron, using Δλ = (h/mₑc)(1 − cosθ), where h is Planck's constant, mₑ is the electron's rest mass, c is the speed of light, and θ is the scattering angle. The term h/mₑc is called the Compton wavelength of the electron (about 2.43 picometers), and the shift is zero at θ=0 and maximal (twice the Compton wavelength) at θ=180°, a direct backscatter.

This 1923 discovery by Arthur Compton was historically decisive evidence that light behaves as discrete particles (photons) carrying momentum, not just waves, and it's a staple topic in quantum mechanics and modern physics courses. Enter the scattering angle to find the resulting wavelength shift.