Question

The emissivity of a body of surface area $5c{m}^2$ and radiating 300J of energy per minute at temperature ${727}^{o}C$ is :

• A. 0.48
• B. 0.38
• C. 0.28
• D. 0.18

Answer 1

Answer: (D)

0.18

Energy radiated, $P=eA\sigma T^4$

$e=\frac{P}{A\sigma T^4}=\frac{300/60}{5\times {10}^{-4}\times 5.67\times {10}^{-8}(1000{)}^4}=0.18$