A) Newton?s law of cooling
B) Stefan?s law of radiation
C) Provost?s theory
D) Kirchhoff?s law
Correct Answer: D
Solution :
According to Kirchhoff?s law the ratio of emissive power to absorptive power is same for all surfaces at the same temperature and is equal to the emissive power of a perfectly black body at that temperature. Hence, \[\frac{{{e}_{1}}}{{{a}_{1}}}=\frac{{{e}_{2}}}{{{a}_{2}}}=....{{\left[ \frac{E}{A} \right]}_{perfectly\,black\,body}}\] Now, since \[{{({{E}_{\lambda }})}_{black}}\]is constant at a given temperature, this implies that good absorber is a good emitter (or radiator).
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