Do all chiral objects rotate the plane of polarization of EM waves? For example my hand is chiral, will it rotate the plane of polarization of EM waves of suitable wavelength?

  • 1
    $\begingroup$ "optical activity" is a problematic term if only because it implies EM radiation in the visible range. Unfortunately there isn't a simple general term. Though you could say, "can chiral macroscopic objects rotate the plane of EM waves of a suitable wavelength?" $\endgroup$
    – matt_black
    Jan 12, 2021 at 13:59

2 Answers 2


Of course it will, provided you have a billion of it. (One molecule does not rotate much, after all.) Also, each should come without the rest of the body, or at least without the other hand, otherwise that would make a racemic mixture. (I'll leave the grisly details to the reader's imagination.) Also, each hand should form the same gesture, otherwise the destructive interference will ruin the effect.

Also, light of suitable wavelength would be microwave radiation, and a cursory search seems to indicate that the methods of polarizing it and measuring its polarization are known.

With all these conditions fulfilled, I don't see any difference from the situation with the molecules and ordinary light.

  • $\begingroup$ Slightly off-topic, but I wonder if it's possible to formalise some concept of "maximising chirality", such that a single interaction between a chiral photon and a chirally-maximised object would be significantly different depending on the relative chiralities. With molecules this may be hard to investigate smoothly, but perhaps macroscopic objects could be more freely adjusted and studied. $\endgroup$ Jan 10, 2021 at 10:28
  • $\begingroup$ Screw-shaped things like helicenes come to mind. $\endgroup$ Jan 10, 2021 at 10:52
  • $\begingroup$ and some types of achiral liquid crystal forming molecules have chiral helical phases. $\endgroup$
    – porphyrin
    Jan 10, 2021 at 12:56
  • $\begingroup$ Human hand is a macroscopic object, even if there are billions, they will not rotate light. Optical rotation is a molecular phenomenon not a macroscopic phenomenon. $\endgroup$
    – AChem
    Jan 10, 2021 at 17:16
  • $\begingroup$ Microwave radiation is not exactly light. $\endgroup$ Jan 10, 2021 at 17:23

The wavelength has to be comparable with the object size in order to see those effects. Your macroscopic hand will not rotate ordinary light even if you have millions hands around, because the wavelength of light is so small. Yes, it will scatter light as a large object. This idea of optical rotation by long wavelengths and by large objects was shown more than 100 years ago by J.C. Bose, using twisted pieces of jute (a type of rope made from plants). Bose was in India and jute was a common material there to play around.

See this article.


  • $\begingroup$ I think you got the the 'Bose's mixed up. The Bose whose you're referring to is JC Bose, who was the one who did many experiments with EM waves. The other Bose is SN Bose who made contributions to Quantum Mechanics.(Bose-Einstein) $\endgroup$
    – user102687
    Jan 11, 2021 at 17:43
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    $\begingroup$ You are right Milan. I corrected it. $\endgroup$
    – AChem
    Jan 11, 2021 at 17:47

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