JEE Main · 2024 · 31 Jan 2024 · Shift 2 · Modern Physics

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In a photoelectric effect experiment a light of frequency 1.5 times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:

(A)Doubled
(B)Quadrupled
(C)Zero✓ Correct
(D)Halved

Answer: (C)

Solution

The threshold frequency is

f_{0}

, and the incident light initially has

f = 1.5 f_{0}

.

When the frequency is halved, the new frequency is

f^{'} = \frac{f}{2} = 0.75 f_{0}

Since

f^{'} < f_{0}

, each photon now carries less energy than the material's work function, so no electron can be ejected regardless of how high the intensity is raised. The number of photoelectrons emitted is zero.

JEE Main · 2024 · 31 Jan 2024 · Shift 2 · Single correct option

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