Optical activity refers to the ability of chiral molecules to rotate plane-polarized light due to the interaction of electric fields with electron clouds. When an optical wave polarizes the electron clouds, it induces a shift in electron density, resulting in emitted electrical fields that can rotate the polarization axis. This rotation occurs because the symmetry of the molecule affects how the polarization is oriented, leading to a non-isotropic response in the emitted fields. Understanding these interactions is crucial for grasping the physical mechanisms behind optical activity.
PREREQUISITESChemists, physicists, and students studying molecular optics or chiral substances will benefit from this discussion, particularly those interested in the mechanisms of optical activity and its applications in various fields.
DrDu said:The electric fields of the optical wave polarize the electron clouds. The moving polarization of the electron clouds in turn leads to electrical fields which are partially emitted. However, the electric fields are not always emitted at the same point where the polarization and currents have been induced. If the resultant fields are furthermore rotated with respect to the incoming wave due to the low symmetry of the molecule, the polarization axis of the resultant field will be rotated.
Electric fields exert forces on the electrons and oppositely on the nuclei. Hence the centers of charge will separate and you will get a polarisation varying with the frequency of the incoming light. However, if the molecule isn't symmetrical, the polarisation will not be strictly along the direction of the incoming field. Hence the field of the fluctuating dipoles will be tilted as compared to the incoming field, i.e. the plane of polarisation gets rotated.Vivek des said:How does the electron cloud gets polarized?