Wien's displacement law. Graph showing the change in the peak wavelength (horizontal axis, in nanometres) with energy density (vertical axis) for black body thermal radiation. The temperature for each graph is given with a text label in degrees Kelvin. As the temperature decreases (here from 5500 Kelvin to 3500 Kelvin), the peak wavelength increases. This inverse relationship is known as Wien's displacement law, and was derived in 1893 by the German physicist Wilhelm Wien (1864-1928). The term Wien's displacement law also refers to the overall changes with temperature.