A black body is at 7270C. It emits energy at a rate which is proportional to

Amount of heat energy radiated per second by unit area of a back body is directly proportional to fourth power of absolute temperature.According to Stefan's law,           E ∝ T4or E = σT4where σ is a constant of proportionality and called Stefan's constant. Its value is5.67 × 10-8Wm-2K-4Hence E ∝ (727 +273)4 E= ∝(1000)4