Physics · Atomic Physics

JEE Main 2024 — 4 April, Shift 2 — Question 44

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

Assertion A : Number of photons increases with increase in frequency of light.

Reason R : Maximum kinetic energy of emitted electrons increases with the frequency of incident radiation.

In the light of the above statements, choose the most appropriate answer from the options given below :

Option A:
Both $\mathbf{A}$ and $\mathbf{R}$ are correct and $\mathbf{R}$ is NOT the correct explanation of $\mathbf{A}$ .
Option B:
$\mathbf{A}$ is correct but $\mathbf{R}$ is not correct.
Option C:
Both $\mathbf{A}$ and $\mathbf{R}$ are correct and $\mathbf{R}$ is the correct explanation of $\mathbf{A}$ .
Option D:
$\mathbf{A}$ is not correct but $\mathbf{R}$ is correct.
Correct

Answer: D

Intensity of light $\mathrm{I}=\frac{\mathrm{nh} v}{\mathrm{~A}}$

Here n is no. of photons per unit time.

$\mathrm{n}=\frac{\mathrm{IA}}{\mathrm{h} v}$ so on increasing frequency $v, \mathrm{n}$ decreases taking intensity constant.

$\mathrm{k}_{\max }=\mathrm{h} v-\phi$

So on increasing $v$ , kinetic energy increases.

Answer key and solution verified before publishing.

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