A black body at $227^{\circ} \mathrm{C}$ radiates heat at the rate of $7 \mathrm{cals} / \mathrm{cm}^2 \mathrm{~s}$. At a temperature of $727^{\circ} \mathrm{C}$, the rate of heat radiated in the same units will be :

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Aicharya · Accepted Answer

$\begin{aligned} &\text {Key Idea Apply Stefan's law of radiation. }\ & \mathrm{M} / \mathrm{E} =\sigma \mathrm{T}^4 \ & \frac{\mathrm{E}_1}{\mathrm{E}_2} =\left[\frac{\mathrm{T}_1}{\mathrm{~T}_2}\right]^4 \ & \Rightarrow \mathrm{E}_2 =7\left[\frac{273+727}{273+227}\right]^4 \ & =\left(\frac{1000}{500}\right)^4 \times 7 \ & =112 \mathrm{cal}-\mathrm{cm}^{-2} \mathrm{~s}^{-1} \end{aligned}$

A black body at $227^{\circ} \mathrm{C}$ radiates heat at the rate of $7 \mathrm{cals} / \mathrm{cm}^2…

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