A black metal foil is warmed by radiation from a small sphere at temperature `T` and at a distance d it is found that the power received by the foil is `P` If both the temperature and the distance are doubled the power received by the foil will be .

Options

A. P
B. 2P
C. 8P
D. 4P

Answer

D

Explanation

Power received `prop (T^(4))/(r^(2)) rArr P prop (T^(4))/((r)^(2)), P' prop ((2T)^(4))/((2r)^(2))® " " rArr (P')/P=16/4 rArr P'=4P`