# Does the colour (wavelength) of the light change, when it enters an optically denser medium?

Light passes through the ocular fluid of our eye, after passing through the lens of the eye, before striking our cones. Irrespective of what medium it passes through, we will always perceive the same color? Thus, does it matter, what medium it passes through?

The wavelength does change, but the color does not.

Because color is more properly linked to frequency and frequency remains the same. Yes, I know, many sources link it to wavelength but if they want to do that they should be linking it to vacuum wavelength.

Here's why you should consider color as a function of frequency:

• You eye responds to photons according to their energy because the complex molecules that are visual pigments get excited through certain ranges in energy.

• Quantum mechanically the energy is linked to frequency by $$E = h f \;,$$ rather than to wavelength (which affects momentum).

• But aren't wavelength and frequency conversely related. As the wavelength increases, the frequency decreases proportionally. – zane scheepers Mar 28 '17 at 0:12
• Frequency and vacuum wavelength are linked by $f=c/\lambda$. In a medium, the $c$ changes to $v$, so the relationship depends on the medium. – The Photon Mar 28 '17 at 0:17
• Thanks. So if f is constant, for c to change, the wavelength has to change. I'm curious though. How do you know that the cones respond to frequency and not wavelength? – zane scheepers Mar 28 '17 at 0:27
• Zane: these are quantum transitions between bound states, just like changes in electron orbitals in a simple atom. Those changes depend on energy. – dmckee --- ex-moderator kitten Mar 28 '17 at 0:33
• The color of light doesn't change, but the color of some objects (diffraction jewels) will. Color is an ambiguous word... – Whit3rd Mar 28 '17 at 4:45

I could be wrong here - but I once had a physics book about microscopes & optical techniques, that said that some polarization occurs in most crystalline media as there are many internal "faces", which changes the energy & therefore the color, when some energy is shifted towards the polarized plane direction, but the effect we see is subtle, - I can't find the reference right now. Hope this helps, I'll be back if I find my source!