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Q.
A black body is at $727^{\circ} C$. It emits energy at a rate which is proportional to
Thermal Properties of Matter
Solution:
Amount of heat energy radiated per second by unit area of a black body is directly proportional to fourth power of absolute temperature.
According to Stefan's law,
$E \propto T^{4}$
or $E=\sigma T^{4}$
where $\sigma$ is constant of proportionality and called Stefan's constant. Its value is
$5.67 \times 10^{-8} Wm ^{-2} K ^{-4}$
Hence $E \propto(727+273)^{4}$
$E=\propto(1000)^{4}$