The absorptivity of a body is equal to its emissivity _________________?
Correct answer: D. Under thermal equilibrium
- A. At a particular temperature
- B. For circular bodies
- C. None of these
- D. Under thermal equilibrium
Explanation
Kirchhoff’s law of thermal radiation states that absorptivity equals emissivity when a body is in thermal equilibrium with its surroundings. This condition, not shape, is essential.
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