Find the critical angle for glass of refractive index $1.5$.
A$48.6^\circ$
B$30^\circ$
C$33.7^\circ$
D$41.8^\circ$CORRECT
JUPEBPhysicsWaves and Optics
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Why the answer is D, and why the others tempt you.
$\sin C = \dfrac{1}{n} = \dfrac{1}{1.5} = 0.667$, so $C = \sin^{-1}(0.667) \approx 41.8^\circ$. Using $\tan$ instead of $\sin$ gives 33.7, and $48.6$ is the critical angle for water ($n = 1.33$).
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