In discussing calcite, we pointed out that its large birefringence arises from the fact that the carbonate groups lie in parallel planes (normal to the optic axis). Show in a sketch and explain why the polarization of the group will be less when vector E is perpendicular to the CO₃ plane than when vector E is parallel to it. What does this mean with respect to v_⊥ and v_||, that is, the wave’s speeds when vector E is linearly polarized perpendicular or parallel to the optic axis?