question_answer

The heat radiated per unit area in 1 hour by a furnace whose temperature is 3000 K is \[(\sigma =5.7\times {{10}^{-8}}W\,{{m}^{-2}}{{K}^{-4}})\]                                             [JEE ONLINE 07-05-2012]

A) \[1.7\times {{10}^{10}}J\]

B)      \[1.1\times {{10}^{12}}J\]

C) \[2.8\times {{10}^{8}}J\]         

D)      \[4.6\times {{10}^{6}}J\]

Correct Answer: A

Solution :

[a] According to Stefan9 slaw

Heat radiated per unit area in 1 hour (3600s)

is