The radiant energy from the sun, incident normally at the surface of earth is 20 kcal/m2 min. What would have been the radiant energy, incident normally on the earth, if the sun had a temperature, twice of the present one?
(a) 320 kcal/m2 min.
(b) 40 kcal/m2 min.
(c) 160 kcal/m2 min.
(d) 80 kcal/m2 min.
