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(a) Why photoelectric effect can not be ...

(a) Why photoelectric effect can not be explained on the basis of wave nature of light ? Give reasons.
(b) Write the basic features of photon picture of electromagnetic radiation on which Einstein's photoelectric equation is based.

Text Solution

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(a) According to wave theory.
(i) The maximum kinetic energy of the emitted electron should be directly proportional to the intensity of incident radiations but it is not observed experimentally. Also maximum kinetic energy of the emitted electrons should not depend upon incident frequency according to wave theory, but it is not so.
(ii) Electron emission should take place at all frequencies of radiations i.e., there should not exist the threshold frequency. This fact contradicts experimental observation.
(iii) There should be a time lag in photo-electric emission but according to observation photoelectric emission is instantaneous.
(b) According to photon picture :
(i) Each quantum of radiation has energy hv.
(ii) In photo-electric effect the electrons in the metal absorbs this quantum of energy (hv).
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