A black body is an object that absorbs 100% of all incoming radiation. It reflects no radiation and appears perfectly black. It is a theoretical object; therefore in practice, no known material has been found capable of absorbing all incoming radiation.

Some materials, however, are capable of absorbing almost all of its incoming radiation. Carbon in its graphite form, for instance, absorbs 97%

Black bodies are also perfect emitters of radiation. At a particular temperature and frequency, black bodies emit the maximum possible amount of energy for that temperature and frequency. This value of energy is called black body radiation.

Black bodies emit at every wavelength of light, in order to absorb every wavelength and therefore all incoming radiation. The maximum wavelength emitted by a black body radiator is infinite. The amount of energy which black bodies emit at each wavelength for a particular temperature is a definite amount.