Assertion : Photoelectric effect supports the quantum nature of light.
Reason : Photoelectric emission is instantaneous.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To analyze the given assertion and reason, we will break down the concepts involved in the photoelectric effect and how they relate to the quantum nature of light.

### Step 1: Understand the Assertion
The assertion states that "Photoelectric effect supports the quantum nature of light." This is true because the photoelectric effect demonstrates that light can behave as particles (photons) which carry quantized energy. When light of a certain frequency strikes a metal surface, it can eject electrons if the frequency is above a certain threshold. This supports the idea that light has a particle-like nature, which is a key aspect of quantum mechanics.

**Hint:** Consider how the photoelectric effect illustrates the particle nature of light.

### Step 2: Understand the Reason
The reason states that "Photoelectric emission is instantaneous." This is also true; when light of sufficient frequency hits a metal surface, electrons are emitted almost immediately (within about \(10^{-10}\) seconds). This instantaneous emission indicates that the energy from the photons is transferred to the electrons very quickly, allowing them to overcome the work function of the metal.

**Hint:** Think about the time scale of the photoelectric effect and how it relates to the emission of electrons.

### Step 3: Analyze the Relationship
While both the assertion and the reason are true, the reason does not adequately explain the assertion. The assertion is about the quantum nature of light, while the reason focuses on the speed of the emission process. The instantaneous nature of the emission does not directly support the claim that the photoelectric effect demonstrates the quantum nature of light.

**Hint:** Reflect on whether the reason provides a direct explanation for the assertion.

### Conclusion
Thus, the assertion is true, and the reason is also true, but the reason does not correctly explain the assertion. Therefore, the correct conclusion is that while both statements are valid, the relationship between them does not hold.

**Final Answer:** Assertion is true; Reason is true, but Reason does not explain Assertion.

### Summary of Steps:
1. Understand the assertion about the quantum nature of light.
2. Understand the reason regarding the instantaneous nature of photoelectric emission.
3. Analyze the relationship between the assertion and the reason.