Assertion : The frequencies of incident, reflected and refracted beam of monochromatic light are same.
Reason : The incident, reflected and refracted rays are coplanar.

Options

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

Explanation

To solve the question, we need to analyze the assertion and reason provided.

### Step 1: Analyze the Assertion
The assertion states that "The frequencies of incident, reflected, and refracted beam of monochromatic light are the same."

- **Explanation**: Monochromatic light means light of a single wavelength and frequency. When light interacts with a boundary (like air to glass), the frequency of the light does not change. This is because frequency is determined by the source of the light, and since all three beams (incident, reflected, and refracted) originate from the same source, they will have the same frequency.

### Step 2: Analyze the Reason
The reason states that "The incident, reflected, and refracted rays are coplanar."

- **Explanation**: Coplanarity means that the rays lie in the same plane. This is a true statement in the context of light rays interacting with a surface. However, this fact about coplanarity does not explain why the frequencies of the rays are the same. The frequency being the same is due to the nature of monochromatic light and its source, not because the rays are coplanar.

### Step 3: Conclusion
- **Assertion**: True (frequencies are the same).
- **Reason**: True (rays are coplanar).
- **Correct Explanation**: The reason provided does not correctly explain the assertion.

Thus, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer
The correct option is B: Both assertion and reason are true, but reason is not the correct explanation of the assertion.

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