These question consists of two statements each printed as Assertion and Reason. While answering these question you are required to choose any one of the following five responses.
Assertion: Emissive power of a perfectly black body is one.
Reason: Absorptive power of perfectly black body is one.

Options

A. If both Assertion and Reason are correct and Reason is also a good absorber of radiation at a given wavelength.
B. If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C. If Assertion is true but Reason is false
D. If Assertion is false but Reason is true.

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states: "Emissive power of a perfectly black body is one."
- Emissive power (E) is defined as the ability of a body to emit radiation compared to a perfect black body at the same temperature. For a perfect black body, the emissive power is indeed 1 (or 100% efficiency in emitting radiation). Therefore, this assertion is **true**.

2. **Understanding the Reason**:
- The reason states: "Absorptive power of a perfectly black body is one."
- Absorptive power (A) is defined as the ratio of energy absorbed by the body to the energy incident on it. A perfect black body absorbs all incident radiation, which means its absorptive power is also 1. Thus, this reason is also **true**.

3. **Evaluating the Relationship**:
- Both the assertion and the reason are true statements. However, the assertion is not a direct consequence of the reason. They are related concepts in thermodynamics, but one does not prove the other.

4. **Choosing the Correct Response**:
- Since both the assertion and reason are true, but the assertion does not directly follow from the reason, we conclude that the correct response is that both are true, but the assertion does not support the reason.

### Conclusion:
The correct option is that both the assertion and reason are true, but the assertion does not explain the reason.