 When polarized light interacts with a molecule, it distorts the molecule which induces an equal and opposite effect in the plane-wave, causing it to be rotated by the difference between the orientation of the molecule and the angle of polarization of the light wave.If ρ ≥ formula_9, then the vibrations at that frequency are "depolarized"; meaning they are not totally symmetric.At least 25 variations of Raman spectroscopy have been developed.