An ideal thermal source of radiation. It produces continuous spectra with a characteristic shape, in which the peak wavelength depends on the temperature of the source, in accordance with Wien's Law. A characteristic of sources that produce spectra that are close to the black-body form is that there is a high degree of interaction between EM radiation and the material that makes up the source. This leads to the formal definition of a black body, which has the property of absorbing perfectly any electromagnetic radiation that is incident on it and emitting a black-body spectrum – the Planck curve. [[../Chapters/Part 1 The spectral continuum]]