Radiation of frequency 10 15 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.
Surface C: photo emission occurs and photoelectrons have some kinetic energy. Using Einstein’s photo-electric equation, explain the three observations.
Answer:
From the observations made (parts A and B) on the basis of Einstein’s photoelectric equation, we can draw following conclusions:
- For surface A, the threshold frequency is more than 10 15 HZ, hence no photoemission is possible.
- 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.
- For surface C, the threshold frequency is less than 10 15 Hz. So photoemission occurs and photoelectrons have some kinetic energy
