Optical rotation or optical activity:
Optical rotation or optical activity is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it passes through specific materials ofr fluids. Optical activity occurs only in chiral materials, those have no microscopic mirror symmetry. Optical activity can be observed in fluids. It can also be observed in chiral solids.
The rotation of the plane of polarization may be either clockwise, to the right (dextrorotary — d-rotary), or to the left (levorotary — l-rotary) depending on which stereoisomer is present (or dominant). For a given substance, the angle by which the polarization of light of a specified wavelength is rotated is proportional to the path length through the material and (for a solution) proportional to its concentration.Optical activity is measured using a polarized source and polarimeter.
