Planck’s constant h is fundamental to Quantum Mechanics. But what is Planck’s constant?
Separating the fundamental units from h, it is found to be equal to a distance multiplied by a momentum. If then we consider using the speed of light, c and a given mass, we arive at a new parameter equalling a distance. This parameter is the Compton wavelength of a particle.
The Compton wavelength of light:
Compton wavelength of an electron:
Physicists had considerable difficulty accepting the existence of the photon. For one, it introduced the non-deterministic nature which collided with classical mechanics and it also went against Maxwell’s theories, which at the time were considered highly successful. The concept of Compton Scattering was one of the final pieces of support that lead to a wider acceptance of the photon as a particle.
Compton Scattering provided an image of a photon literally colliding with an electron, showing that like the electron, the photon was worthy of being considered a particle as well. The classical version of Compton Scattering was Thompson Scattering, which considered the photon as a wave. The Thompson Scattering experiment applied a photon wave to an electron, which caused the electron to be energized and radiate a photon wave.
Compton Scattering, treating the photon as a particle provides a different picture at higher energy levels: