What is the stopping potential?

The correct answer is Option (1) → For a particular frequency of the incident radiation, the minimum negative (retarding) potential given to the collector plate for which the photocurrent stops or becomes zero.

Option (1) For a particular frequency of the incident radiation, the minimum negative (retarding) potential given to the collector plate for which the photocurrent stops or becomes zero. — Correct. With the collector made negative, the photoelectrons are repelled and only the more energetic ones reach it. At the stopping potential \( V_0 \) even the most energetic photoelectrons are turned back, so the photocurrent becomes zero and \( K_{\mathrm{max}}=eV_0 \).

Option (2) Photocurrent does not depend upon the intensity of light. — Incorrect. This is not a definition of the stopping potential. The statement is also wrong. The photocurrent is directly proportional to the intensity, because brighter light ejects more electrons per second.

Option (3) Photocurrent depends upon the frequency of the incident light. — Incorrect. This is a statement about the photocurrent. It does not define the stopping potential. For radiations of different frequencies but the same intensity, the saturation current is the same. It is the stopping potential that changes with frequency.

NCERT (2026-27):
Effect of Potential on Photoelectric Current – “… The photocurrent is found to decrease rapidly until it drops to zero at a certain sharply defined, critical value of the negative potential V₀ on the plate A. 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.”