Critical angle from glass to air
What is the critical angle for light passing from glass (n = 1.5) into air?
Answer B: explanation for every choice
A
30° is arcsin(0.5), the critical angle for n = 2.
B
Correct. sin θc = n₂/n₁ = 1/1.5 = 0.667, so θc ≈ 41.8°.
C
This uses arccos(0.667) instead of arcsin.
D
56.3° is arctan(1.5), the Brewster angle for polarization.
Takeawaysin θc = n₂/n₁, which is possible only when going from higher to lower n.
Equation usedCritical angle
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