The work of Davisson and Germer helped to explain light's
ability to propagate through a vacuum. They designed and built a vacuum
apparatus for the purpose of measuring the energies of electrons scattered from
a metal surface. Electrons from a heated filament were accelerated by a voltage
and allowed to strike the surface of nickel metal. They observed that at certain angles, there
was a peak in the intensity of the scatters electron beam. The peak indicated
wave behavior for the electrons.
