Question

Two spheres of the same material have radii $1m$ and $4m$ and temperatures $4000K$ and $2000K$ respectively. The ratio of energy radiated per second is

• A. 1
• B. 2
• C. 4
• D. None of these

Answer 1

Answer: (A)

1

Ratio of energy radiated per second

$\frac{P_1}{P_2}=\frac{e\sigma A_1{T_1}^4}{e\sigma A_1{T_2}^4}$

$=\frac{(1{)}^2}{(4{)}^2}\frac{(4000{)}^4}{(2000{)}^4}=\frac{1}{1}$