A Simple Device for Exploring Optical Activity Available to Purchase

When plane-polarized light passes through an optically active material, the plane of polarization is rotated. The angle of rotation depends on the material, its temperature, and the wavelength of the light. It may also be affected by the electric and magnetic fields to which the sample is subjected. In this paper we describe a simple spinning analyzer technique that may be used to study the optical activities of materials. After passing through the sample, a polarized light beam is directed through a continuously rotating polarizing sheet (analyzer). A light detector is used to sense the intensity of the light exiting the analyzer, and the resulting signal may be displayed on an oscilloscope or computer screen and observed by many students simultaneously. With our setup we can make continuous measurements of the rotation angle and can also impressively demonstrate Malus' law.