The plane of vibration of linearly polarized light rotates as it propagates through a medium This rotation can occur in either a right or left handed direction Since linearly polarized light can be regarded as the sum of right and left hand circularly polarized components, this optical activity corresponds to different indices of refraction for the two circular components(circular birefringence)
A property caused by asymmetrical molecular structure that enables a substance to rotate the plane of incident polarized light. Ability of a substance to rotate the plane of polarization of a beam of light passed through it, either as crystals or in solution. Clockwise rotation as one faces the light source is "positive," or dextrorotary; counterclockwise rotation "negative," or levorotary. Louis Pasteur was the first to recognize that molecules with optical activity are stereoisomers (see isomerism). Optical isomers occur in pairs that are nonsuperimposable mirror images of one another. They have the same physical properties except for their effect on polarized light; in chemical properties they differ only in their interactions with other stereoisomers (see asymmetric synthesis)