For the electron, the lightest particle around to scatter from,
For the electron, the lightest particle around to scatter from,
Compare to 500 nm for light, so not much effect for visible light. We need light of wavelength, say 0.02 nm, to get a big effect. Light of this wavelength we call “X-rays” discovered by Roentgen in 1895. They can be nicely diffracted by the planes of atoms in a crystal, and that is how Compton supplied the wave-type measurement before and after scattering.