There are several characteristics of the photoelectric effect that conflict with the wave model of light. It's important to understand where these inconsistencies come from by considering what we would actually expect to see in this model and why we would expect this. So what would we see?

In the wave model, light is an electromagnetic wave that can propagate through a vacuum at a speed of 300,000,000 m/s and transfers a continuous stream of energy. The energy this wave delivers per unit area per unit time - its intensity - depends only on the amplitude. From this we can outline some expected observations:

  • We expect the kinetic energy (speed) of the photoelectrons and the number of them emitted per unit time to increase with the light intensity.
  • Because intensity does not depend on frequency, changing the frequency should have no effect on the kinetic energy (speed) of the photoelectrons and the photoelectric effect should occur for any frequency of light.
  • At lower intensities, it will take a longer time for the total energy absorbed by the surface to exceed the work function. At low enough intensities, we should then see a measurable delay between the activation of the light source and the first photoemission.