JEE MAIN - Physics (2025 - 29th January Morning Shift - No. 22)
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Emission of electrons in photoelectric effect can be suppressed by applying a sufficiently negative electron potential to the photoemissive substance.
Reason (R) : A negative electric potential, which stops the emission of electrons from the surface of a photoemissive substance, varies linearly with frequency of incident radiation.
In the light of the above statements, choose the most appropriate answer from the options given below :
Explanation
Assertion (A) is true because a sufficiently negative potential can repel and stop the emitted electrons from leaving the surface.
Reason (R) is also true because the stopping potential $V_{\text{stop}}$ varies linearly with the frequency $\nu$ of the incident light ($V_{\text{stop}} = \frac{h}{e}\,\nu - \frac{\phi}{e}$).
However, (R) does not directly explain why a negative potential suppresses electron emission; it only shows how much potential is needed for different frequencies.
Therefore, both (A) and (R) are true, but (R) is not the correct explanation of (A).
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