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Question : 24
Total: 37
Light of same wavelength is incident on three photo-sensitive surfaces A, B and C. The following observations are recorded.
(a) From surface A, photoelectrons are not emitted.
(b) From surface B, photoelectrons are just emitted.
(c) From surfaceC
Compare the threshold frequencies of the three surfaces and justify your answer.
OR
If the frequency of light incident on the cathode of a photocell is increased, how will following be affected? Justify your answer.
(i) Energy of the photo electrons
(ii) Photo current
(a) From surface A, photoelectrons are not emitted.
(b) From surface B, photoelectrons are just emitted.
(c) From surface
Compare the threshold frequencies of the three surfaces and justify your answer.
OR
If the frequency of light incident on the cathode of a photocell is increased, how will following be affected? Justify your answer.
(i) Energy of the photo electrons
(ii) Photo current
Solution:
(a) From surface A, electron is not emitted. So, the value of threshold frequency more than the frequency of the incident radiation.
(b) From surface B, photoelectrons are just emitted. So, the value of threshold frequency is equal to the frequency of the incident radiation.
(c) From surfaceC
Threshold frequency is defined as the minimum frequency of light which causes electron emission from a metal surface. No electron emission, means that the frequency of the light is less than the threshold frequency and electron emission means that the frequency of the light is more than the threshold frequency.
OR
If the frequency of light incident on the cathode of a photocell in increased then
(i) Energy of the photo electron increases
(ii) Rate of electron emission remains same. Hence the current remains same.
(b) From surface B, photoelectrons are just emitted. So, the value of threshold frequency is equal to the frequency of the incident radiation.
(c) From surface
Threshold frequency is defined as the minimum frequency of light which causes electron emission from a metal surface. No electron emission, means that the frequency of the light is less than the threshold frequency and electron emission means that the frequency of the light is more than the threshold frequency.
OR
If the frequency of light incident on the cathode of a photocell in increased then
(i) Energy of the photo electron increases
(ii) Rate of electron emission remains same. Hence the current remains same.
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