Read the following features of the Photoelectric effect.
(A) The maximum kinetic energy of the photoelectrons varies linearly with the frequency of incident radiation
(B) The maximum kinetic energy of the photoelectrons is dependent on its intensity.
(C) For a frequency of incident radiation, lower than the cut-off frequency, photoelectric emission is possible even if the intensity is not large.
(D) Ultraviolet light can eject photoelectrons from copper even if visible light does not eject
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (D) only
Einstein's photoelectric equation is \( K_{\max} = h\nu - \phi_0 \).
(A) The maximum kinetic energy of the photoelectrons varies linearly with the frequency of incident radiation. — Correct. \( K_{\max} = h\nu - \phi_0 \) is a straight line in \( \nu \).
(B) The maximum kinetic energy of the photoelectrons is dependent on its intensity. — Incorrect. It depends on the frequency and the metal only. Intensity changes the number of photoelectrons, not their maximum energy.
(C) For a frequency of incident radiation, lower than the cut-off frequency, photoelectric emission is possible even if the intensity is not large. — Incorrect. Below the threshold frequency no emission occurs, however intense the light is. A photon has too little energy to free an electron.
(D) Ultraviolet light can eject photoelectrons from copper even if visible light does not eject. — Correct. Ultraviolet has a higher frequency than visible light and can exceed the threshold frequency of copper, which visible light cannot.
NCERT (2026-27):
Effect of Frequency of Incident Radiation on Stopping Potential – “… (iii) For a given photosensitive material, there exists a certain minimum cut-off frequency of the incident radiation, called the threshold frequency, below which no emission of photoelectrons takes place, no matter how intense the incident light is. 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).”