Q. Two spherical bodies of same materials having radii 0.2 m and 0.8 m are placed in same atmosphere. The temperature of the smaller body is 800 K and temperature of the bigger body is 400 K . If the energy radiated from the smaller body is E, the energy radiated from the bigger body is (assume, effect of the surrounding temperature to be negligible),
A) 16 E
B) E
C) 64 E
D) 256 E
Explanation
[Solution by Dr. Abubacker] Radiated energy $\propto AT^4\propto r^2T^4$: $\frac{E_b}{E_s}=\left(\frac{0.8}{0.2}\right)^2\left(\frac{400}{800}\right)^4=16\cdot\frac1{16}=1$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.