Why optically active compounds rotate plane polarised light?
Answers
according to me,
Linear polarization may be expressed as a superposition of two opposite circular polarizations. And the polarization direction depends on the phase difference of the two circular polarizations. In simple words: imagine a situation where you add two vectors that rotate with the same angular velocity in different directions, both having the same amplitude. Their sum is the vector that oscillates in a constant direction.
Imagine now a coil spring. Note that it looks the same when you turn it. Hence If you take a "heap" if such springs, everyone pointing in a random direction, still they all exhibit a sort of an anisotropy. This is chirality.
If a circularly-polarized EM field propagates through the media consisting of such "springs" - it's likely that the interaction will be different for right/left handed polarizations.
Imagine that the interaction is elastic. Effectively this "slows down" the EM wave, however two circularly-polarized components are affected differently. Hence, after passing through the media, the phase difference of the two components will change. Hence the superposition of those two components will still be linearly-polarized, but the direction will change...
tysm------------@kundan