Q. The surface area of a black body is $5 \times 10^{- 4}\ m^{2}$ and its temperature is 727$℃$ . the energy radiated by it per minute is ($\sigma = 5.67 \times 10^{- 8}\ Jm^{- 2} - s^{- 1} - K^{- 4})$

A) $1.7 \times 10^{3}$ J
B) $2.5 \times 10^{2}$ J
C) $8 \times 10^{3}$ J
D) $3 \times 10^{4}$ J
Explanation

(a) From Stefan’s law
$E = \sigma T^{4}A$
Given, $T = 727℃ = (727 + 273) = 1000$ K
$\ \ \ \ \ \ \ \ \ A = 5 \times 10^{- 4}\ m^{2}$
$\therefore\ \ \ \ Energy = \left( 5.67 \times 10^{- 8} \right)(1000)^{4}\left( 5 \times 10^{- 4} \right)60$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ E = 1.7 \times 10^{3}$ J

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.