State Stefan-Boltzmann law.

Explanation

Stefan-Boltzmann law states that the total amount of heat radiated per second per unit area of a black body is directly proportional to the fourth power of its absolute temperature.
`E alpha T^(4)` or `E=sigmaT^(4)`
where `sigma` is known as Stefan's constant. Its vale is `5.67xx10^(-8)Wm^(-2)k^(-4)`.