Question
A ray of light travels from glass (n=1.5) to air (n=1).
For which angle of incidence will the ray just graze the surface (total internal reflection limit)?Solution
The critical angle θC for total internal reflection is: θC = sin-1 (n₂/n₁) = sin-1 (1/1.5) = sin-1 (0.666….) ≈ 41.8° At this angle, the refracted ray grazes the interface. Hence, the correct answer is 41.8°.
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