Assertion: Photoelectric effect proves the particle nature of light.
Reason: Photoemission starts as soon as light is incident on the metal surface, provided frequency of incident light is greater than or equal to the threshold frequency.

Options

A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason or true but Reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Answer

To analyze the given assertion and reason, we can break down the solution into the following steps:

### Step 1: Understand the Assertion
The assertion states that the photoelectric effect proves the particle nature of light. This is true because the photoelectric effect demonstrates that light can be thought of as consisting of particles called photons. When light of sufficient frequency strikes a metal surface, it can eject electrons from that surface.

**Hint:** Consider how the photoelectric effect demonstrates the quantization of light energy.

### Step 2: Understand the Reason
The reason provided states that photoemission starts as soon as light is incident on the metal surface, provided the frequency of the incident light is greater than or equal to the threshold frequency. This is also true. The threshold frequency is the minimum frequency required for the incident light to have enough energy to eject electrons from the metal.

**Hint:** Recall the relationship between frequency, energy, and the threshold frequency in the context of the photoelectric effect.

### Step 3: Connect the Assertion and Reason
Both the assertion and reason are true statements. The reason correctly explains the assertion because the photoelectric effect, which is the phenomenon being described, requires that the frequency of the incident light meets or exceeds the threshold frequency for photoemission to occur.

**Hint:** Think about how the conditions for the photoelectric effect validate the particle nature of light.

### Step 4: Conclusion
Since both the assertion and reason are true, and the reason provides a correct explanation for the assertion, we conclude that the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

**Final Answer:** Option A: Both assertion and reason are true, and the reason is the correct explanation of the assertion.