Question

Given below are two statements:
Assertion (A): In photoelectric effect there is no time lag \((\sim10^{-9}s)\) between incidence of photon and emission of photoelectrons.
Reason (R): This is because electromagnetic wave energy is concentrated in photons and not spread out, so there should be no delay in the emission of electrons.

• 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)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Instantaneous emission in photoelectric effect is explained by photon theory of light.

Answer 1

The Correct Option is A

Concept:
Photoelectric effect supports the particle nature of light. Light energy is absorbed by electrons in the form of photons.

Step 1: Check Assertion.
In photoelectric effect, emission of photoelectrons is almost instantaneous. \[ A \text{ is correct} \]

Step 2: Check Reason.
The energy of light is concentrated in photons. A single photon transfers its energy to an electron. \[ R \text{ is correct} \]

Step 3: Check explanation.
Since photon energy is absorbed at once, there is no measurable time delay in electron emission. \[ R \text{ correctly explains } A \] \[ \therefore \text{Correct Answer is (A)} \]