Practice portal › Ray Optics and Optical Instruments › Refraction and Total Internal Reflection
Asked in GUJCET 2015 · Snell's law, slabs and apparent depth
Given: light crossing from a rarer into a denser medium.
Idea: the source fixes the frequency f; a medium cannot swallow or create wavefronts, so the same f passes through.
For any wave v = fλ.
In the denser medium the speed is v = c/n, which is smaller.
Since f is unchanged, λ = v/f must shrink in exactly the same ratio.
So the velocity falls because the wavelength changes.
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