ABSTRACT
A cold solid body does not produce any emissions, but with increasing temperature, it begins to become brighter and changes colour. A black body is a theoretical object, which absorbs 100% of the radiation that arrives on it. A black body heated to a sufficiently high temperature emits radiation. The study of the properties of black body radiation played a key role in the development of quantum physics. The history of the black body begins around 1860 when Kirchhoff defines what is meant by black body and formulates some general laws on its properties. Planck began to work on a cavity model where the walls were composed of resonators, that is, by electrically charged harmonic oscillators capable of exchanging energy with the electromagnetic radiation. In 1905, Einstein confirmed the idea of Planck explaining the photoelectric effect and showing that the radiation is not only emitted, but also absorbed in the form of packets or photons.
