A black body at $227^o C$ radiates heat at the rate of $7\; cals/cm^2 s$. At a temperature of $727^o C$, the rate of heat radiated in the same units will be
AIPMT 2009, Medium
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Rate of heat radiated at $(227+273)\,K$
$=7\,cals/(cm^2s)$
Let rate of heat radiated at $(727+273)\,K=x\,cals/(cm^2s)$
By $Stefan's\,law,\,7\propto(500)^4\,and\,x\propto(1000)^4$
$\therefore \frac{x}{7} = {2^4} \Rightarrow x = 7 \times {2^4} = 112\,cals/\left( {c{m^2}s} \right).$
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