Optical activity of oriented molecules

The established theory of optical activity relates the activity to the mean electric dipole induced by the time-derivative of the magnetic field of the light wave and to the associated mean magnetic dipole induced by the time-derivative of the electric field. The results is adequate for the interpretation of the average activity in an isotropic medium, but not for components of the activity along different molecular axes. The theory is extended to include the effects of the electric dipole induced by the electric field gradient of the electromagnetic wave as well as that of the electric quadrupole induced by the electric field. The resulting expression for any component of the optical activity is independent of the choice of origin.