How does the Compton effect provide evidence that X-rays behave as photons?

The Compton effect provides compelling evidence for the particle nature of X-rays by demonstrating that they behave as discrete photons capable of colliding with electrons like material particles.12

In 1922, Arthur Holly Compton successfully explained the scattering of X-rays by treating the interaction as a collision between an individual photon and a loosely bound electron. By applying the laws of conservation of energy and conservation of momentum to these collisions, Compton showed that the photon transfers a portion of its energy and momentum to the electron, causing the electron to recoil.12

Because the incident photon loses energy during this collision, the scattered photon must have a lower frequency and, consequently, a longer wavelength. This shift in wavelength, which depends on the scattering angle, was confirmed through experimental measurements. This successful theoretical treatment, which relies on the assumption that radiation consists of granular quanta, serves as a cornerstone of quantum mechanics and provides definitive proof of the particle-like behavior of electromagnetic radiation.123