The momentum of a photon is given by:

p

=

h l

In 1923, Louis de Broglie predicted that since light exhibited both wave and particle behavior, particles should also. He proposed that all particles have a wavelength given by the equation above. For particles we can write this as:

l

=

h mv

Every particle has a de Broglie wavelength, but the wave properties of matter are only observable for very small objects.

de Broglie wavelength of a human being running at top speed: 1 x 10^-36 m

de Broglie wavelength of a 10 eV electron: 3.9 x 10^-10 m, comparable to the spacing between atoms.