Q. A black body radiates $20\ W$at temperature $227℃$. If temperature of the black body is changed to $727℃$ then its radiating power will be
A) $120\ W$
B) $240\ W$
C) $320\ W$
D) $360\ W$
Explanation
(c) For a black body $\frac{Q}{t} = P = A\sigma T^{4}$
$\Rightarrow \frac{P_{2}}{P_{1}} = \left( \frac{T_{2}}{T_{1}} \right)^{4} \Rightarrow \frac{P_{2}}{20} = \left( \frac{273 + 727}{273 + 227} \right)^{4}$
$\Rightarrow \frac{P_{2}}{20} = (2)^{4} \Rightarrow P_{2} = 320W$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.