JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Modern Physics

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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: The photoelectric effect does not take place, if the energy of the incident radiation is less than the work function of a metal.
Reason R: Kinetic energy of the photoelectrons is zero, if the energy of the incident radiation is equal to the work function of a metal.
In the light of the above statements, choose the most appropriate answer from the options given below.

(A)Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$
(B)Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$ ✓ Correct
(C) $A$ is correct but $R$ is not correct
(D) $A$ is not correct but $R$ is correct

Answer: (B)

Solution

Assertion A is correct: photoelectric effect requires incident photon energy

h ν \geq W_{0}

(work function). Reason R is also correct: from Einstein's photoelectric equation

h ν = W_{0} + K E_{ma x}

, when

h ν = W_{0}

, the maximum kinetic energy is zero. However, R does not explain A — A concerns the threshold condition for emission, while R describes the kinetic energy at threshold. Both are independent correct statements.

JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Single correct option

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JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Modern Physics

Solution

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