Radiation of frequency 1015 Hz is incident on three photosensitive surfaces A, B and C………….

Question 14:Radiation of frequency 1015 Hz is incident on three photosensitive
surfaces A, B and C. Following observations are recorded:
Surface A: no photoemission occurs
Surface B: photoemission occurs but the photoelectrons have zero
kinetic energy.3
Surface C: photo emission occurs and photoelectrons have some
kinetic energy.
Using Einstein’s photo-electric equation, explain the three
observations.

The correct answer is -From the observations made (parts A and B) on the basis of Einstein’s
photoelectric equation, we can draw following conclusions:
1. For surface A, the threshold frequency is more than 1015 HZ,
hence no photoemission is possible.
2. For surface B the threshold frequency is equal to the frequency of
given radiation. Thus, photo-emission takes place but kinetic
energy of photoelectrons is zero.
3. For surface C, the threshold frequency is less than 1015 Hz. So
photoemission occurs and photoelectrons have some kinetic
energy