Choose the correct statements among the following about the photoelectric effect.
(A) For a given photosensitive material and frequency of incident radiation above the threshold frequency, the photoelectric current increases linearly with the increase in intensity of incident light.
(B) Magnitude of stopping potential increases with the increase in the frequency of incident radiation above the threshold frequency.
(C) Both photoelectric current and magnitude of stopping potential increase with the increase in intensity of incident light.
(D) There is no apparent time lag between the incidence of light and ejection of electrons from the photosensitive material.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (D) only
In the photoelectric effect the number of emitted electrons depends on the intensity of light, while their maximum kinetic energy depends only on the frequency: \( eV_{0} = h\nu - \phi_{0} \).
(A) For a given photosensitive material and frequency of incident radiation above the threshold frequency, the photoelectric current increases linearly with the increase in intensity of incident light. — Correct. The number of photons, and hence of photoelectrons, is proportional to the intensity.
(B) Magnitude of stopping potential increases with the increase in the frequency of incident radiation above the threshold frequency. — Correct. \( V_{0} = (h/e)\nu - \phi_{0}/e \) increases linearly with \( \nu \).
(C) Both photoelectric current and magnitude of stopping potential increase with the increase in intensity of incident light. — Incorrect. The current increases, but the stopping potential is independent of intensity; it depends only on \( \nu \) and the metal.
(D) There is no apparent time lag between the incidence of light and ejection of electrons from the photosensitive material. — Correct. Emission is practically instantaneous (within about \( 10^{-9}\ \mathrm{s} \)), since one photon gives its energy to one electron at once.
NCERT (2026-27):
Effect of Intensity of Light on Photocurrent – “… It is found that the photocurrent increases linearly with intensity of incident light as shown graphically in Fig. 11.2.”
Effect of Frequency of Incident Radiation on Stopping Potential – “… Above the threshold frequency, the stopping potential or equivalently the maximum kinetic energy of the emitted photoelectrons increases linearly with the frequency of the incident radiation, but is independent of its intensity (Fig. 11.5).”
Effect of Frequency of Incident Radiation on Stopping Potential – “… (iv) The photoelectric emission is an instantaneous process without any apparent time lag (~10−9 s or less), even when the incident radiation is made exceedingly dim.”