A black body at a temperature of `227^(@)C` radiates heat at a rate of `20 cal m^(-2)s^(-1)`. When its temperature is raised to `727^(@)C` the radiated by it in cal `m^(-2)s^(-1)` will be closet to

Options

A. `120 W`
B. `240 W`
C. `320 W`
D. `360 W`

Answer

C

Explanation

For a black body `Q/t = P = A sigma T^(4)`
`rArr (P_2)/(P_1) = ((T_2)/(T_1))^(4) rArr (P_2)/(20) = ((273+727)/(273+227))^(4)`
`rArr (P_2)/(20) = (2)^(4) rArr P_(2)=320W`