Optical rotation is the phenomenon where the plane of polarized light is rotated when it passes through certain substances, such as sugar solutions or chiral compounds. This rotation occurs due to the interaction between the light and the molecular structure of the substance, which can be either clockwise (dextrorotatory) or counterclockwise (levorotatory). The degree of optical rotation depends on several factors, including the concentration of the solution, the length of the path the light travels through the substance, and the specific properties of the chiral molecules involved. Optical rotation is commonly measured using an instrument called a polarimeter.