The radiant energy from the Sun incident normally at the surface of earth is `20kcal//m^(2)` min What would have been the radiant energy incident normally on the earth if the sun had a temperature twice of the present one ? .

Options

A. 160k `cal//m^(2)` min
B. 40k `cal//m^(2)` min
C. 320k `cal//m^(2)` min
D. 80k `cal//m^(2)` min

Answer

C

Explanation

According to Stefan.s law, `E prop T^(4)`
`(E_(1))/(E_(2))=(T_(1)^(4))/(T_(2)^(4)) or (20)/(E_(2))= (T^(4))/(2^(4)T^(4)) rArr E_(2)=320 kcal//m^(2)`. min.