A black body is an idealized description of a radiation source in theoretical physics. It describes a cavity that contains electromagnetic radiation of a certain temperature. The idea of *black body radiation* is to describe the spectrum of said radiation. ![[blackbody_spectrum.excalidraw.light.svg]] When physicists like Wilhelm Wien, John Rayleigh or James Jeans tried to explain the observed data, they did not find good agreement across the whole range (red and blue curve on the right side). Only when Max Planck assumed that energy was transmitted in [[Discreteness|discrete]] packages, he could fit the whole data range (black curve on the right). He had to introduce an energy quantum. A fact that he was not happy with at all. For his discovery, he got the 1918 Nobel prize. This was one of the first signs that classical physics was not sufficient as a theory. Another experiment that hinted at problems with the wave nature of light was the [[Photo-electric Effect|photo-electric effect]]. >[!read]- Further Reading > - [[Discreteness]] > - [[Quantum Mechanics]] > - [[Photo-electric Effect]] >[!ref]- References >- M. Planck, _Über eine Verbesserung der Wien’schen Spectralgleichung_ (J.A. Barth, Leipzig, 1900). >- W. Wien, Ueber die Energievertheilung im Emissionsspectrum eines schwarzen Körpers, Annalen Der Physik **294**, 662 (1896). >- M. K. E. L. Planck, Zur Theorie des Gesetzes der Energieverteilung im Normalspectrum, Verhandl. Dtsc. Phys. Ges. **2**, (1900).