Question

The surface area of a black body is $5\times {10}^{-4}{m}^2$ and its temperature is ${727}^{o}C$. The amount of radiation emitted by it per minute will be

• A. 0.17 J
• B. 17 J
• C. 170 J
• D. 1701 J

Answer 1

The correct option is D 1701 J

The power radiated is given by Stefan's law:
$P=\sigma Ae{T}^4$
Stefan-Boltzmann constant: $\sigma =5.67\times {10}^{-8}W{m}^{-2}{K}^{-4}$
$A=5\times {10}^{-4}{m}^2$
Temperature, T $={727}^{\circ }C=1000K$
$e=1$ for a black body
$P=5.67\times {10}^{-8}\times 5\times {10}^{-4}\times 1\times (1000{)}^4=28.35W$

Heat lost in one minute $=60\times 28.35=1701J$