If the wavelength of light in an experiment on photoelectric effect i…

The correct answer is Option (1) → (B) and (D) only

Emission needs the photon energy \( hc/\lambda \) to exceed the work function; the stopping potential follows from Einstein's photoelectric equation.

    \( \displaystyle eV_s = \frac{hc}{\lambda} - \phi_0 \)

Increasing \( \lambda \) lowers the photon energy \( hc/\lambda \).

(A) the photoelectric emissions will not take place — Incorrect. Emission stops only if \( \lambda \) goes beyond the threshold wavelength; for a small increase it continues.

(B) the photoelectric emission may or may not take place — Correct. It depends on whether the new wavelength is still below the threshold wavelength.

(C) the stopping potential will increase. — Incorrect. A smaller photon energy lowers the maximum kinetic energy, so the stopping potential falls.

(D) the stopping potential will decrease — Correct. \( V_s = (hc/\lambda - \phi_0)/e \) decreases as \( \lambda \) increases (whenever emission still takes place).

Statements (B) and (D) are correct, which is Option (1).

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.”