A black body at a temperature of 227 ° C radiates heat at the rate of 5 cal c m - 2 s - 1 . At a temperature of 727 ° C the rate of heat radiated per unit area in cal c m - 2 s - 1 is

Step-by-step solution

According to Stefan's law radiant energy emitted by a perfectly black body per unit area per sec ( i e , emissive power of black body) is directly proportional to the fourth power of its absolute temperature ie E ∝ T 4 ⇒ E 1 E 2 =   T 1 4 T 2 4 5 E 2 =   ( 273 + 227 ) 4 ( 273 + 727 ) 4   E 2 = 5 × 1000 500 4   =   5 × 16 = 80   c a l   c m - 2 s - 1