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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:

1. (A) is false but (R) is true.
2. (A) is true but (R) is false.
3. Both (A) and (R) are true and (R) is the correct explanation of (A).
4. Both (A) and (R) are true but (R) is not the correct explanation of (A).

Correct answer: Both (A) and (R) are true but (R) is not the correct explanation of (A).

Solution

The assertion is true because applying a negative potential can indeed prevent electrons from being emitted in the photoelectric effect. However, the reason provided is incorrect as the stopping potential does not vary linearly with frequency; it is proportional to the energy of the incident photons, which is related to frequency.

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