The stefan-boltzmann law can be employed to estimate the rate of radiation of energy h from a surface, as in 4 (m'), the emissivity h aeot where h is in watts, a = the surface area that characterizes the emitting properties of the surface (dimensionless), o 5.67 x 10 wm k), andt е a universal constant -8 -2 absolute temperature = 0.90, and t= 650 20 k called the stefan-boltzmann constant (k).