I learned about the refractive index of gases and dense materials, which is a function of the atom number per volume, wavelength of electromagnetic wave, etc. However, what is the refractive of solutions that contains ions? Is it the same as conductors or dielectrics and why? In my point of view, the mass of ions are much larger than electrons and we can neglect their vibration induced by electromagnetic wave. So we can treat the solution the same way as those without ions (such as sucrose solution), am I right?

  • $\begingroup$ Book Bottcher, "theory of electric polarization", if you can get it, mine is out of reach now. I am not sure; your heavy- atom idea should work, but ions imply also dipoles, so change in orbitals of electrons, so different refractive index $\endgroup$ – patta Apr 16 at 17:24
  • $\begingroup$ Well I googled "refractive index salt water" and it changes from 1,33 to 1,38 with or without salt, that is very little difference $\endgroup$ – patta Apr 16 at 17:27
  • $\begingroup$ Hi @patta, I've got this book. Yes you are right the refractive index do changes. Actually I made a very sensitive sensor that can detect even weaker refractive index change. Thanks for your reply. $\endgroup$ – Fengfeng Apr 16 at 18:52
  • $\begingroup$ I will look tomorrow at what Bottcher said.. $\endgroup$ – patta Apr 16 at 19:45
  • $\begingroup$ What is confusing me is that since ions move freely in solutions, then how can we select electric dipoles? If we choose a single ion which contains positive and negative charges, then it's not electrical neutral. This violates the definition of electric dipoles. If we choose different ions with opposite charges, then which pair of ions should we choose. $\endgroup$ – Fengfeng Apr 16 at 20:10

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