Q. Two spheres made of same material have radii in the ratio$1\ :2$. Both are at same temperature. Ratio of heat radiation energy emitted per second by them is
A) 1 : 2
B) 1 : 4
C) 1 : 8
D) 1 : 16
Explanation
(b) $\frac{E_{1}}{E_{2}} = \frac{A_{1}}{A_{2}}.\left( \frac{T_{1}}{T_{2}} \right)^{4} = \frac{4\pi r_{1}^{2}}{4\pi r_{2}^{2}}\ \times 1 = \left( \frac{1}{2} \right)^{2} = \frac{1}{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.