Physics

This is the Compton effect—a collision between a photon and a stationary electron where the photon loses energy and its wavelength increases. The key insight is that you can treat this as an elastic collision problem: apply conservation of momentum and energy to find how much the wavelength shifts based purely on the scattering angle $\theta$. The result reveals that photons, like particles, carry momentum $p = h/\lambda$.

This is the Compton effect—a collision between a photon and a stationary electron where the photon loses energy and its wavelength increases. The key insight is that you can treat this as an elastic collision problem: apply conservation of momentum and energy to find how much the wavelength shifts based purely on the scattering angle $\theta$. The result reveals that photons, like particles, carry momentum $p = h/\lambda$.