How would the stopping potential for a given photosensitive surface change if (i) the frequency……………..

Question :How would the stopping potential for a given photosensitive surface change if (i) the frequency of the incident radiation were increased? and (ii) the intensity of incident radiation was decreased ” Justify your answer.

The correct answer is -(i) The stopping potential for a given photosensitive surface would increase if the frequency of the incident radiation is increased. This is because the stopping potential is directly proportional to the frequency of the incident radiation according to the photoelectric effect equation: K_max = hf – Φ, where K_max is the maximum kinetic energy of the photoelectrons, h is Planck’s constant, f is the frequency of the incident radiation, and Φ is the work function of the metal. Therefore, as the frequency of the incident radiation increases, the stopping potential required to stop the photoelectrons increases, and the kinetic energy of the emitted photoelectrons decreases.

(ii) The stopping potential for a given photosensitive surface would not be affected by the decrease in the intensity of the incident radiation. This is because the stopping potential depends only on the frequency of the incident radiation and not on its intensity. The number of photoelectrons emitted from the surface is directly proportional to the intensity of the incident radiation, but the kinetic energy of the photoelectrons is determined solely by the frequency of the incident radiation. Therefore, decreasing the intensity of the incident radiation would decrease the number of emitted photoelectrons, but it would not affect their kinetic energy or the stopping potential.

Justification: The stopping potential for a given photosensitive surface depends on the kinetic energy of the emitted photoelectrons, which is determined by the frequency of the incident radiation and the work function of the metal. Therefore, increasing the frequency of the incident radiation would increase the stopping potential, while decreasing the intensity of the incident radiation would not affect the stopping potential, as it depends only on the frequency of the radiation.