Black body

Summary

A black body is an idealised body that absorbs all electromagnetic radiation that falls on it, at every wavelength and from every direction. In equilibrium at a given temperature, no body emits more thermal radiation than it does. Its spectrum is given by Planck's law. Its total emitted power follows the Stefan–Boltzmann law, and real surfaces are described by comparing them with it through their emissivity. The study of black-body radiation led Planck to the quantum hypothesis.