# What is occuring on the quantum level when a molecule rotates plane polarized light?

What is occuring on the quantum level when a molecule rotates plane polarized light?

Also, why do enantiomers then rotate light in opposite directions? I would think that the electromagnetic waves would interact with the transient electric and magnetic fields within the molecule itself as it propagates and therefore the light changes direction as it passes through the molecule. However with this idea there seems to be a problem with the fact that all the molecules wouldn't be oriented in the same directions and thus scatter the light in all directions rather than a net rotation in one direction of the light. I am looking for an explanation using electromagnetism if it can be explained at that level or if it cannot, the quantum mechanical answer would be fine as well.

• Possible duplicate of Molecular chirality and optical rotation – Mithoron Oct 11 '17 at 12:39
• This definitely isn't a duplicate. – pentavalentcarbon Oct 11 '17 at 12:40
• I agree with @pentavalentcarbon. The post Mithoron linked is related to part of your question (why does the random orientation of a solution not cancel out the net rotation), but it doesn't address the physical mechanism by which optical rotation occurs. – Tyberius Oct 11 '17 at 14:00
• I'm not sure if it counts as a duplicate if it's on a different SE, but see how do optically active compounds rotate plane polarized light. – a-cyclohexane-molecule Oct 12 '17 at 3:24
• @a-cyclohexane-molecule A version of that answer in terms a chemist could understand would make a decent answer here (especially if you can avoid any quantum mechanics or math). – matt_black Oct 12 '17 at 11:23

As mentioned in the comments, the answer to your $2^{nd}$ question regarding why optical rotation isn't simply cancelled out in solution due to random orientations is given in ManishEarth's answer to Molecular chirality and optical rotation