Wilhelm Wien formulates Wien's displacement law

Background. Wien's displacement law states that black-body radiation curves peak at different wavelengths depending on temperature. The peak wavelength is inversely proportional to absolute temperature, meaning higher temperatures result in shorter wavelengths. This relationship was established through thermodynamic arguments, linking the spectral brightness of radiation to thermal conditions.

Derivation. Wien derived the law in 1893 using a thermodynamic argument based on Boltzmann's reasoning. The law describes how the entire spectrum of black-body radiation shifts toward shorter wavelengths as temperature increases. This derivation relied on the concept of adiabatic invariance, which was instrumental for later developments in quantum mechanics.

Significance. The law is named for Wilhelm Wien, who deduced it theoretically in 1893. It relates the peak wavelength emitted by a body to its temperature. Although Planck later formulated a more general equation, Wien's law remains useful for connecting emission peaks to thermal conditions, predating the full understanding of black-body radiation functions.