How does polarimeter measure optical rotation?

To measure optical rotation, a Light Emitting Diode (LED) produces a beam of ordinary light. This light first passes through a polarizer (polarization filter) in order to obtain a defined orientation of the plane of polarization. The polarized light then passes through the sample cell.

What is optical rotation method?

Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. ... Optical activity is measured using a polarized source and polarimeter.