Question

The threshold frequencies (f) of three metals A,B and C are in the order f_A>f_B>f_C. If light of frequency lesser than f_C is incident on the metal surfaces, then
1. Only A and B will undergo photoelectric emission
2. A, B and C will undergo photoelectric effect
3. Only A will undergo photoelectric emission
4. None of A, B, and C will undergo photoelectric effect

Answer 1

Correct Answer - Option 4 : None of A, B, and C will undergo photoelectric effect

The correct answer is option 4) i.e. None of A, B, and C will undergo photoelectric effect.

CONCEPT:

• Threshold frequency: It is the minimum frequency of incident radiation below which the photoelectric emission will not occur.
• Photoelectric effect: The photoelectric effect is a phenomenon where electrons are ejected from a metal surface when the light of sufficient frequency is incident on it.

EXPLANATION:

​​​​Given that: fA>fB>fC

• For the photoelectric effect to occur, the frequency of incident radiation must be greater than the frequency of each of the metal surfaces.
• When the light of frequency lesser than fC is incident on the metal surfaces, none of the three metal surfaces will undergo photoelectric emission as this frequency is lesser than the threshold frequency values of A, B, and C.