Kirchhoff's Laws of Radiation

Kirchhoff's Laws of Radiation describe how objects emit and absorb thermal radiation. They state that at thermal equilibrium, a perfect black body (an ideal absorber and emitter) emits the maximum possible radiation at each wavelength for its temperature. Furthermore, a good absorber at a given wavelength will also emit radiation efficiently at that wavelength, making emission and absorption directly related. In essence, objects that absorb well at a certain wavelength also radiate well at that same wavelength, helping explain the balance of energy exchange through thermal radiation in nature.