State the Stefan ? Boltzmann law of radiation. Express its mathematical form.
Solution
The Stephan-Boltzmann Law describes the power radiated a body that absorbs all radiation that falls on its surface in terms on its temperature. The radiation energy per unit time from a black body is proportional to the fourth power of the absolute temperature and can be expressed with Stefan-Boltzmann Law as: The Stefan-Boltzmann Constant.
Radiate energy = (Emissivity) (Stefan-Boltzmann constant) (Temperature)4 (Area)
The equation is:
P = є σ T4 A
P: Radiate energy
σ: The Stefan-Boltzmann Constant
T: absolute temperature in Kelvin
є: Emissivity of the material.
A: Area of the emitting body