Compton Shift Calculator

About this calculator

This calculator finds the Compton wavelength shift, Δλ = λ_c(1 − cos θ), that occurs when a photon scatters off a free electron and loses energy — where λ_c is the electron's Compton wavelength (h/mₑc ≈ 2.426 pm) and θ is the scattering angle. Discovered experimentally by Arthur Compton in 1923, this shift is measurable only in high-energy photons like X-rays and gamma rays, and it was decisive proof that light behaves as discrete particles (photons) carrying momentum, not just waves.

The Compton effect is central to X-ray physics and medical imaging (it accounts for a major source of image scatter and dose in radiography and CT), astrophysics (Compton scattering shapes the spectra of X-ray sources and the early universe's photon-baryon interactions), and radiation detector design in particle physics.

Physics students studying quantum mechanics and wave-particle duality, medical physicists modeling radiation dose and scatter, and researchers working with X-ray or gamma-ray spectroscopy all use this calculation, entering the scattering angle to find the wavelength shift.