What is optical rotary dispersion?

Optical rotatory dispersion (ORD) describes that the optical rotation of a substance changes with the wavelength of light that passes through it. In this case, smaller wavelengths lead to a greater optical rotation with the same path traveled by the light.

In polarimetry the higher rotation of short wavelength can be helpful when dealing with small sample volumes. The higher rotation can compensate the shorter distance the light travels through the small sample.