Each enantiomer of a chiral structure reacts differently with polarized light. Polarized light is shown above. It is light were only one plane of polarization is chosen by a polarization filter (slit). When this light is travelling through a chiral substance, the plane of rotation will change. In the example above, R-(-)-carvone has a angle of rotation of -72°, S-(+)-carvone one of +72 °.
This animation was written by Marco Ziegler, previously of the Chemistry Departement of Fribourg University.