Planck radiation law
A law that defined blackbody radiation better than its predecessor, therefore resolving the ultraviolet catastrophe. It is depend on the supposition that electromagnetic radiation is quantized.
At thermodynamic temperature T, for a blackbody, the radiancy R onto a range of frequencies among nu & nu + dnu is provided by
R = 2 pi h nu^{3}/[c^{3} [exp (h nu/k T) ^{- 1}]].