The wave model of light does not explain what?

Answer 1

It does not explain the photoelectric effect.

According to the wave theory, given light of sufficient intensity, electrons should be emitted from the surface of a metal.

What is observed though, is that given light of sufficient frequency, electrons will be emitted from the metal surface independent of intensity. If the frequency is too low, electrons will NOT be emitted even if the highest intensity of light was used.

Albert Einstein suggested that it would be possible to explain the photoelectric effect if light was considered to be made up of particles instead of waves. The energy of the particles of light, called photons, would be proportional to the frequency of the light.

Electrons would be emitted from the metal only if the energy of ONE photon was sufficient for the electron on the metal surface to break bonds and escape from the surface. Otherwise, the photons will rebound on the metal surface with no emission of electrons.

Einstein 'mathematised' the photoelectric effect in the following equation:

hf = Ekmax + o

where

h is the planck constant

f is the frequency of the radiation

Ekmax is the maximum kinetic energy of the emitted electrons

o is the work-function energy, that is the minimum energy required for the electron to escape from the metal surface.

Note: hf is the energy of a photon.

It was for the explanation of the photoelectric effect that Einstein was awarded the Nobel prize in Physics in 1921. (and not for his still greater discoveries in relation to relativity)

Answer 2

the photoelectric effect