I shone a green laser light(~532 nm) through a glass slab and what I saw inside was that the light beam was now red. Imagine a regular refraction diagram but color the beam outside green and that on the inside red.
As frequency doesn't change upon entering another medium, effective light velocity in a medium becomes directly proportional to that of wavelength. So, as speed decreases shouldn't wavelength also do so? But in this case, it increases. Or is this logic wrong?
Also, it can't be due to light losing energy.
What is happening in here?