Question

If a black body emits $0.5J$ of energy per second when it is at ${27}^{o}C,$ then the amount of energy emitted by it when it is at ${627}^{o}C$ will be :

• A. $162J$
• B. $135J$
• C. $40.5J$
• D. $13.5J$

Answer 1

Answer: (C)

$40.5J$

According to Stefan's law,

$E\propto T^4$

$\frac{E_1}{E_2}={\left[\frac{T_1}{T_2}\right]}^4$

$\frac{E_1}{0.5}={\left[\frac{273+627}{273+27}\right]}^4$

$E_1=0.5{\left[\frac{900}{300}\right]}^4$

$E_1=40.5J$