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Assertion : Emissivity of any body (e) i...

Assertion : Emissivity of any body (e) is always less than its absorptive power (a).
Reason : Both the quantities are dimensionless.

A

If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.

B

If both Assertion and Reason are 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.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question, we need to analyze both the assertion and the reason provided. ### Step 1: Understanding the Assertion The assertion states that the emissivity (e) of any body is always less than its absorptive power (a). - **Emissivity (e)** is defined as the ratio of the energy radiated by a body to the energy radiated by a black body at the same temperature. - **Absorptive power (a)** is defined as the ratio of the energy absorbed by the body to the total energy incident on it. ### Step 2: Evaluating the Assertion According to Kirchhoff's law of thermal radiation, for any body in thermal equilibrium, the emissivity (e) is equal to the absorptive power (a). Therefore, the assertion that e is always less than a is incorrect. - **Conclusion**: The assertion is **false**. ### Step 3: Understanding the Reason The reason states that both emissivity and absorptive power are dimensionless quantities. - Both emissivity and absorptive power are indeed dimensionless because they are ratios of similar quantities (energy), which means they do not have any units. ### Step 4: Evaluating the Reason Since both quantities are dimensionless, the reason is **true**. ### Final Conclusion - The assertion is **false**. - The reason is **true**. Thus, the correct answer is that the assertion is false, and the reason is true. ### Summary - Assertion: False - Reason: True
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