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Asked in GSEB Board July 2022 · Snell's law, slabs and apparent depth
Given: n₂₁=(n₂)/(n₁)<1, so medium 2 is optically rarer than medium 1.
Idea: Snell's law in this notation is (sin i)/(sin r)=n₂₁.
With n₂₁<1 it follows that sin i<sin r.
Both angles lie between 0° and 90°, where the sine increases, so i<r, that is r>i.
A refracted ray at a larger angle to the normal has swung away from it.
This is the ordinary case of light leaving water or glass for air: it tilts away from the normal, and once i is large enough r reaches 90° and total internal reflection takes over.
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