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Emissive and Absorptive Power

The thermal r...

Question

The thermal radiation emitted by a body is proportional to Tⁿ where T is its absolute temperature. The value of n is exactly 4 for

(a) a blackbody
(b) all bodies
(c) bodies painted black only
(d) polished bodies only

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Solution

(b) all bodies

From Stefan-Boltzmann law, the energy of the thermal radiation emitted per unit time by a blackbody of surface area A is given by
$u = σ A T^{4}$
Here, $σ$ is Stefan-Boltzmann constant.
This law holds true for all the bodies.

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