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:
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:
- (A)(A) is false but (R) is true.
- (B)(A) is true but (R) is false.
- (C)Both (A) and (R) are true and (R) is the correct explanation of (A).
- (D)Both (A) and (R) are true but (R) is not the correct explanation of (A).✓ Correct
Answer: (D)
Solution
Assertion: applying a sufficiently negative potential to the collector repels even the fastest photoelectrons (those with the maximum kinetic energy), so beyond the stopping potential no electron reaches the collector and the photocurrent is suppressed. This is correct.
Reason: the stopping potential is related to the incident frequency by Einstein's photoelectric equation,
which is indeed a linear relation in , so the reason is also correct.
However, the reason only describes how the magnitude of the stopping potential varies with frequency; it does not explain the physical mechanism by which a negative potential suppresses emission (repelling the electrons). So the reason, although true, does not explain the assertion.
Both statements are true, but R is not the correct explanation of A.
Reason: the stopping potential is related to the incident frequency by Einstein's photoelectric equation,
which is indeed a linear relation in , so the reason is also correct.
However, the reason only describes how the magnitude of the stopping potential varies with frequency; it does not explain the physical mechanism by which a negative potential suppresses emission (repelling the electrons). So the reason, although true, does not explain the assertion.
Both statements are true, but R is not the correct explanation of A.
JEE Main · 2025 · 29 Jan 2025 · Shift 1 · Single correct option