Photoelectric Effect -Failure of Wave Theory

Failure of Wave Theory: The various characteristics of the photoelectric effect cannot be explained on the basis of wave theory of light due to these reasons:

(1) According to the wave theory, th energy carried by a light wave is measured by the intensity of the beam. So when light falls on a metal surface, the energy of the wave should be transferred uniformly to the electrons in the surface before they are emitted out. The energy taken up by the electrons must increase as the intensity of light is increased. But it is observed that the maximum energy of the emitted electrons is independent of the light intensity.

(i) According to the wave theory light of any frequency should be able to eject electrons from a surface, provided only that the light is intense enough. Experiment, however, shows that light of frequency lower than a certain threshold value cannot eject photoelectrons, no matter how intense it is.

(iii) According to wave theory, the energy transferred from light waves is not gained by a single electron but is distributed among all the electrons present in the lighted area. Therefore, some time will be elapsed before an electron collects sufficient energy for emission. It means there must be some time lag between the incidence of light radiation and emission of photoelectron. But this is n oo

Thus, wave theory fails in explaining the experimental observations regarding the photoelectric effect.

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