Optical rotatory dispersion

In optics, optical rotatory dispersion is the variation of the specific rotation of a medium with respect to the wavelength of light. Usually described by German physicist Paul Drude's empirical relation:

$${\displaystyle [\alpha ]_{\lambda }^{T}=\sum _{n=0}^{\infty }{\frac {A_{n}}{\lambda ^{2}-\lambda _{n}^{2}}}}$$

where ${\displaystyle [\alpha ]_{\lambda }^{T}}$ is the specific rotation at temperature ${\displaystyle T}$ and wavelength ${\displaystyle \lambda }$, and ${\displaystyle A_{n}}$ and ${\displaystyle \lambda _{n}}$ are constants that depend on the properties of the medium.

Optical rotatory dispersion has applications in organic chemistry regarding determining the structure of organic compounds.