Optical activity refers to the ability of chiral molecules to rotate plane-polarized light, a phenomenon resulting from the interaction of light's electric fields with the electron clouds of these molecules. When light interacts with a chiral molecule, the electric fields polarize the electron clouds, causing a shift in electron density. This polarization creates fluctuating dipoles that emit electrical fields. Due to the low symmetry of chiral molecules, these emitted fields do not align with the incoming light's polarization, resulting in a rotation of the polarization axis. Although molecules in solution can orient in various directions, only certain orientations significantly contribute to the rotation of light, while others can be disregarded. The polarization of the electron cloud occurs as electric fields exert forces on electrons and nuclei, leading to a separation of charge centers, which varies with the light's frequency. This asymmetry in polarization causes the plane of polarization to rotate, explaining the optical activity of chiral substances.
