optically active

Optically active substances are materials that can rotate the plane of polarized light as it passes through them. This property arises from their molecular structure, which is chiral—meaning they have a non-superimposable mirror image, like left and right hands. When polarized light interacts with such molecules, the light's wave oscillations are rotated either clockwise or counterclockwise, depending on the substance. This phenomenon is important in chemistry for identifying and characterizing specific compounds, such as many pharmaceuticals and natural products.