Which of the following statements are correct?
A. Number of photoelectrons emitted per second is directly proportional to the intensity of incident radiation
B. Cut off potential is the minimum negative potential given to the plate for which photocurrent becomes maximum
C. For a given frequency of the incident radiation, the stopping potential is independent of its intensity
D. Even for the exceedingly dim incident radiation apparent time lag is \( \sim 10^{-9}\,\mathrm{s} \) or less
E. Photons are electrically neutral and are not deflected by electric and magnetic fields
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, C, D and E only
The statements test the experimental laws of the photoelectric effect and the photon picture of light.
(A) Number of photoelectrons emitted per second is directly proportional to the intensity of incident radiation — Correct. A higher intensity means more photons per second, and each absorbed photon can free one electron, so the photocurrent is proportional to the intensity.
(B) Cut off potential is the minimum negative potential given to the plate for which photocurrent becomes maximum — Incorrect. The cut-off (stopping) potential is the minimum negative potential at which the photocurrent becomes zero, because it stops even the fastest photoelectrons.
(C) For a given frequency of the incident radiation, the stopping potential is independent of its intensity — Correct. By Einstein's equation \( eV_0 = h\nu - \phi_0 \), the stopping potential depends only on the frequency, not on how many photons arrive.
(D) Even for the exceedingly dim incident radiation apparent time lag is \( \sim 10^{-9}\,\mathrm{s} \) or less — Correct. Emission is instantaneous: a single photon gives its energy to one electron at once.
(E) Photons are electrically neutral and are not deflected by electric and magnetic fields — Correct. A photon carries no charge, so electric and magnetic fields exert no force on it.
NCERT (2026-27):
Effect of Intensity of Light on Photocurrent – “… This implies that the number of photoelectrons emitted per second is directly proportional to the intensity of incident radiation.”
Effect of Potential on Photoelectric Current – “… For a particular frequency of incident radiation, the minimum negative (retarding) potential V0 given to the plate A for which the photocurrent stops or becomes zero is called the cut-off or stopping potential. … Thus, for a given frequency of the incident radiation, the stopping potential is independent of its intensity.”