Question

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

• A. 80
• B. 60
• C. 50
• D. 112

Answer 1

The correct option is D 112

From Stefan- Boltzmann law of radiation

$P\alpha T^4$

$P_1,T_1=500K$

$P_2,T_2=1000K$

$\frac{P_2}{P_1}=(\frac{1000}{500}{)}^4$

$P_1=7$

So$\frac{P_2}{P_1}=16$

Then$P_2=16\ast 7$

Therefore$P_2=112$