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JEE Main 2025 Apr 4 Shift 1, Physics Q10: Introduction and Photoelectric Effect

JEE Main2025Apr 4, Shift 1Physics
Q.

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: In photoelectric effect, on increasing the intensity of incident light the stopping potential increases.

Reason R : Increase in intensity of light increases the rate of photoelectrons emitted, provided the frequency of incident light is greater than threshold frequency.

In the light of the above statements, choose the correct answer from the options given below

  1. A

    Both A and R are true but R is NOT the correct explanation of A

  2. B

    A is false but R is true

  3. C

    A is true but R is false

  4. D

    Both A and R are true and R is the correct explanation of A

Solution

The stopping potential is determined by the maximum kinetic energy of photoelectrons: . It depends only on the frequency of incident light and the work function, not on the intensity. So Assertion A is false.

Intensity is the power per unit area; for monochromatic light, , so a higher intensity means more photons per second and (above threshold) more photoelectrons per second. Reason R is true.

A is false, R is true — option (2).

Concept behind this question

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