# Color of light after refraction

I know that the color of light depends on its wavelength. Also, when light moves from one medium to another, its wavelength changes. The question: So, when light moves from one medium to another does its color change?

• The perception of color is a neuro-biological reaction of the brain to stimuli of receptors on the retina. These receptors absorb a photon and undergo a geometrical change which is registered by the brain as light of a certain color. What is important for the receptor to absorb the light is the energy of the light (or frequency), which does not change after refraction.
– Paul
Commented Nov 19, 2016 at 12:19

Another way of saying Apoorv Potnis's answer is to say that the light's color is defined by the photon energy, and this does not change. Since we always "see" light propagating through the vitreous humor of our eye, the only variable here is the frequency: the medium (vitreous humor) is defined and the wavelength follows. So, when we put our eye into water, or other medium, only the frequency can define the color.

There is another sense wherein the color can change subtly on refraction and that is if broadband (white) light is incident non-normally on an interface. Different wavelengths have different transmission co-efficients defined by the Fresnel Equations, so the frequency spectrum of the transmitted light is changed by the refraction. This effect is most pronounced at highly glancing incidence angles.

I'm giving a link of a similar question in my answer as I don't have enough reputation to comment. Link Does light color change when refracting?

The color we perceive is dependent on frequency and wavelength. The color will not change. What you're not taking into account is the speed of light in the medium. It's not the same $c$ in vacuum. The frequency stays the same. What changes is that speed of light in the refracting medium and as a result the wavelength. This difference for speed is the exact reason we have refractive effects, and I believe this was the observation that led to Snell's Law. In symbols
$λ=c/ν$
where $λ$ is the wavelength and $ν$ is the frequency.