Question

Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K, respectively. The ratio of the energy radiated per second by the first sphere to that by the second is

(a) 1:1

(b) 16 :1

(c) 4:1

(d) 1:9

Answer 1

Correct Option (a) 1:1

Explanation:

Energy radiated per second by a body which has surface area A at temperature I is given by Stefen's law,

E = σAT⁴     [as A πr²]