specific rotation

Specific rotation is a measure of how a substance rotates the plane of polarized light. This phenomenon is known as optical activity. The specific rotation quantifies this rotation by considering the angle of rotation, the light path length, and the substance's concentration or density. It is also dependent on temperature and the wavelength of light used. A positive rotation is called dextrorotatory, and a negative rotation is levorotatory. This property was first observed in quartz crystals and later in liquid solutions of substances like tartaric acid and sugar. Louis Pasteur was the first to link optical activity to the asymmetric arrangement of atoms in molecules.1