Failure of wave theory to explain photoelectric effect
Failure of wave theory to explain photoelectric effect :- Huygen’s wave theory of light failed to explain the photoelectric effect because of the following reasons :-
- According to Wave theory of light, the energy of a beam of light is measured by the intensity of the light. As the intensity of the light increases, the amplitude of the waves and hence energy carried by the waves increases. When a beam of light falls on a metal surface, the energy possessed by the beam will be equally distributed among the electrons and these electrons on accepting energy will get ejected from the metal surface. When the light waves of higher intensity falls on a metal surface, it will impart more energy to the electrons in matter. Hence, the kinetic energy of the emitted electrons increases.
This is contradictory to the experimental facts that the maximum kinetic energy of the emitted electron is independent of the intensity of the incident beam of light.
- According to Wave theory of light, the energy of a wave depends on its intensity and not on its frequency. So according to Wave theory of light, the photoelectric emission is possible from a metal surface by the light waves of all frequencies provided the intensity of light is sufficient to provide the required energy for the emission of electrons. This is against the experimental fact that no photoelectric emission takes place from a metal surface if the frequency of incident radiation is less than the threshold frequency.
- According to the wave theory of light, the energy possessed by the light is uniformly distributed across its advancing wavefronts. Thus, when the beam of light is incident on the metal surface, the energy is equally distributed among all the electrons that fall in the part of the surface of the metal which is illuminated. So the electrons will take some time to accumulate the energy required for their emission from the metal surface. This is also against the experimental fact that the emission of electrons takes place immediately after the incidence of radiation.
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