The sphere of radii 8 cm and 2 cm are cooling. Their temperatures are `127^(@)C` and `527^(@)C` respectively . Find the ratio of energy radiated by them in the same time

Options

A. 0.5
B. 0.06
C. 2
D. 1

Answer

D

Explanation

`QpropT^(4),Qprop` Area i.e. `QpropR^(2)`
`therefore(Q_(1)/Q_(2))=(T_(1)/T_(2))^(4)(R_(1)/R_(2))^(2)=(400/800)^(4)(8/2)^(2)`
`=(1/2)^(4)xx(4/1)^(2)=1/16xx16=1.`