Question

what is Stefan's Law?

Answer 1

The Stefan–Boltzmann law, also known as Stefan's law, states that the total energy radiated per unit surface area of a black body per unit time (also known as the black-body irradiance or emissive power), \(j^\star \) , is directly proportional to the fourth power of the black body's thermodynamic temperature T (also called absolute temperature):
\(j^\star =\sigma T^4\)

For details: http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law