question_answer

                                                           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                        [AIEEE 2002]

A)  \[1:1\]

B)                               \[16:1\]

C)  \[4:1\]              

D)       \[1:9\]

Correct Answer: A

Solution :

[a] Energy radiated per second by a body which has surface area A at temperature T is given by Stefan's law,

Therefore.

(since, bodies are of same material )