C) Photon - particle Collision

'Compton Effect'
(2nd proof of photon theory)

- Light act like particles in collisions with free electrons.

High frequency source (like X-Rays) 

	Photon (after)
Photon transferred energy & momentum to electron

Photon's energy
& momentum decrease
 
= Electron's
 energy & momentum increase.

Momentum photon
= p = h/λ

Which color of light has the greatest momentum?

Violet - Highest f, Smallest λ

**Mass, energy, momentum is conserved.