JEE Main 202529 JanuaryMorning Shift
- Exam
- JEE Main
- Year
- 2025
- Date
- 29 January
- Shift
- Morning Shift
- Subject
- Physics
- Chapter
- Atomic Physics
JEE Main 2025 · 29 January · Morning Shift · Physics · Atomic Physics
Given below are two statements : one is labelled as Assertion (A)...
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 :
Options
- A(A) is false but (R) is true
- B(A) is true but (R) is false
- CBoth ((\mathbf{A})) and ((\mathbf{R})) are true and ((\mathbf{R})) is the correct explanation of ((\mathbf{A}))
- DBoth ((\mathbf{A})) and ((\mathbf{R})) are true but ((\mathbf{R})) is not the correct explanation of ((\mathbf{A}))
Correct answer
D. Both ((\mathbf{A})) and ((\mathbf{R})) are true but ((\mathbf{R})) is not the correct explanation of ((\mathbf{A}))
Step-by-step solution
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 (\left(V_{\text{stop }}=\frac{h}{e} \nu-\frac{\phi}{e}\right)).
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).