The Compton effect, discovered by Arthur H. Compton in 1923, provided compelling evidence that light behaves like particles, not just waves. It describes how X-rays, when they collide with electrons, are scattered and emerge with a longer wavelength (lower energy), while the electrons recoil from the impact.
What Happens in the Compton Effect:
- A high-energy X-ray photon strikes a free or loosely bound electron.
- The photon transfers part of its energy to the electron, which recoils.
- The scattered photon moves off in a different direction with reduced energy (thus, increased wavelength).
Key Observations:
- The change in wavelength depends on the angle of scattering.
- The phenomenon could not be explained by classical wave theory, which predicted no change in wavelength upon scattering.
Why It Matters:
- It supported the idea that light has particle-like properties (photons), confirming quantum theory.
- It helped establish the concept of photon momentum, showing that photons, though massless, carry both energy and momentum.
- The Compton effect is strong evidence for the duality of light — behaving both as waves and particles.
The Compton effect was a milestone in physics, reinforcing the emerging quantum mechanics framework and earning Compton the Nobel Prize in Physics in 1927.