The emissive power of sphere of area 0.04 m² is 0.7 k cal s⁻¹ m⁻². The amount of heat radiated in 20 second is (a) 2.8 k cal s⁻¹ m⁻² (b) 0.28 k cal s⁻¹ m⁻² (c) 5.6 k cal s⁻¹ m⁻² (d) 0.56 k cal s⁻¹ m⁻²

Answer: (d). Heat radiated Q = E× A× t Q = 0.7×0.04×20 = 0.56 kcal So the answer is (d) 0.56 (the unit should be kcal; the unit printed in the options is wrong).

The emissive power of sphere of area 0.04 m² is 0.7 k cal s⁻¹ m⁻²… | MHT CET 2021 (22 Sep, Shift 2)

Q88MHT CET 2021 · 22 SEP · SHIFT 2Easy

Thermal Radiation: Black Body, Stefan & Wien

The emissive power of sphere of area $0.04\text{ m}^{2}$ is $0.7\text{ k cal s}^{-1}\text{ m}^{-2}$ . The amount of heat radiated in 20 second is

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Answer: (d)

Heat radiated $Q = E\times A\times t$
$Q = 0.7\times0.04\times20 = 0.56$ kcal
So the answer is (d) 0.56 (the unit should be kcal; the unit printed in the options is wrong).

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