Point out two distinct features observed experimentally in photoelectr

1.	Point out two distinct features observed experimentally in photoelectric effect which cannot be explained on the basis of wave theory of light. State how the photon picture' of light provides an explanation of these features.
Answer» The two required distinct features are: (i) Maximum K.E. of emitted photo electrons, is independent of the intensity of incident light (of a given frequency). (ii) No photo emission takes place from a given photo emitting surface if the frequency (wavelength) of the incident light is less than (more than) a critical or threshold frequency (wavelength). We can understand these features on the basis of the photon theory as follows . (i) Increases in intensity increases only the number of incident photons but does not increase the energy ( = hv) of these photons . Hence there is no increase in the maximum K.E. of the emitted photo electrons. (ii) No photo emission can take place if the energy of the incident photon (= hv = hc/λ) is less than the work function of the photo emitting surface. Hence, there is a minimum (maximum) critical or threshold frequency (wavelength) for given photo emitting surface.

Point out two distinct features observed experimentally in photoelectric effect which cannot be explained on the basis of wave theory of light. State how the photon picture' of light provides an explanation of these features.

Answer»

The two required distinct features are:

(i) Maximum K.E. of emitted photo electrons, is independent of the intensity of incident light (of a given frequency).

(ii) No photo emission takes place from a given photo emitting surface if the frequency (wavelength) of the incident light is less than (more than) a critical or threshold frequency (wavelength).

We can understand these features on the basis of the photon theory as follows .

(i) Increases in intensity increases only the number of incident photons but does not increase the energy ( = hv) of these photons . Hence there is no increase in the maximum K.E. of the emitted photo electrons.

(ii) No photo emission can take place if the energy of the incident photon (= hv = hc/λ) is less than the work function of the photo emitting surface. Hence, there is a minimum (maximum) critical or threshold frequency (wavelength) for given photo emitting surface.

Point out two distinct features observed experimentally in photoelectric effect which cannot be explained on the basis of wave theory of light. State how the photon picture' of light provides an explanation of these features.

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