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 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`