Question

Two spheres of the same metal have radii $1$ m and $4$ m and temperature $4000K$ and $2000K$ respectively. The ratio of the energy radiated per second by the first to the second is :

• A. 1:1
• B. 1:2
• C. 2:1
• D. 1:4

Answer 1

The correct option is A 1:1

We know that radiation from the surface is given as: $E=ϵ\sigma A{T}^4$
$E\propto r^2{T}^4$
$\frac{E_1}{E_2}=\frac{1\times {4000}^4}{16\times {2000}^4}=\frac{256}{256}=\frac{1}{1}$