1. The problem statement, all variables and given/known data This is just my doubt and not really a question. We know that speed of light changes upon change in medium of propagation. Its wavelength also changes. But its frequency doesn't change. So, does the colour of light change upon change in the medium of propagation? 2. Relevant equations Speed = wavelength x frequency 3. The attempt at a solution Since the speed of light is constant in a particular medium, so colour of light depends upon both, frequency and wavelength. So, I'm not able to figure out which one of them should I consider when looking at the colour of light while the medium changes. Wavelength is changing but frequency isn't!!!!