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 four responses.
Assertion: Absorptive power of any substance is temperature independent. Buit emissive power depends on the temperature.
Reason: Emissive power `alpha T^(4)`

Options

A. If both Assertion and Reason are correct but Reason is the correct explanation of Assertion.
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 and reason question, we will analyze both statements provided:

**Assertion:** Absorptive power of any substance is temperature independent. But emissive power depends on the temperature.

**Reason:** Emissive power is proportional to \( T^4 \).

### Step-by-Step Solution:

1. **Understanding Absorptive Power:**
- Absorptive power (α) of a substance is defined as the ratio of the energy absorbed by the substance to the energy incident on it.
- Mathematically, it is expressed as:
\[ \alpha = \frac{\text{Energy absorbed}}{\text{Energy incident}} \]
- This property is intrinsic to the material and does not change with temperature. Therefore, the assertion that "absorptive power of any substance is temperature independent" is **true**.

2. **Understanding Emissive Power:**
- Emissive power (E) refers to the ability of a substance to emit radiation compared to a black body at the same temperature.
- According to Stefan-Boltzmann law, the emissive power is given by:
\[ E = \sigma T^4 \]
- Here, \( \sigma \) is the Stefan-Boltzmann constant, and \( T \) is the absolute temperature. This shows that emissive power is indeed dependent on the temperature, specifically proportional to the fourth power of the temperature. Hence, the reason that "emissive power depends on the temperature" is also **true**.

3. **Analyzing the Relationship Between Assertion and Reason:**
- The assertion states that absorptive power is temperature independent, which is correct.
- The reason states that emissive power is proportional to \( T^4 \), which is also correct.
- Furthermore, the reason provides a correct explanation for the assertion regarding emissive power's dependence on temperature.

### Conclusion:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion. Therefore, the correct response is:

**Option 1:** Both assertion and reason are true, and the reason is the correct explanation of the assertion.