Identify the correct statement among the following.

The correct answer is Option (2) → Any change in stopping potential will be equal to the change in kinetic energy of emitted photo-electrons divided by the charge of the electron.

Einstein’s photoelectric equation gives the maximum kinetic energy \( K_{\max} = h\nu - \phi_0 \), and the stopping potential is defined by \( eV_0 = K_{\max} \).

Option (1) Maximum kinetic energy of the photo-electrons depends on the intensity of the radiation incident on a photo-sensitive surface. — Incorrect. \( K_{\max} \) depends on the frequency of the light and the work function, not on the intensity; intensity changes only the number of photoelectrons (the current).

Option (2) Any change in stopping potential will be equal to the change in kinetic energy of emitted photo-electrons divided by the charge of the electron. — Correct. From \( eV_0 = K_{\max} \), any change gives \( e\,\Delta V_0 = \Delta K_{\max} \), so \( \Delta V_0 = \Delta K_{\max}/e \).

Option (3) Photons of higher energy have longer wavelengths. — Incorrect. \( E = hc/\lambda \): higher energy means a shorter wavelength.

Option (4) Photoelectric current is possible when the frequency of incident radiation is smaller than the threshold frequency of the metal. — Incorrect. No photoelectrons are emitted below the threshold frequency, however intense the light.

NCERT (2026-27):
Effect of Potential on Photoelectric Current – “… Photoelectric current is zero when the stopping potential is sufficient to repel even the most energetic photoelectrons, with the maximum kinetic energy (\( K_{\max} \)), so that

    \( \displaystyle K_{\max} = eV_0 \qquad (11.1) \)”