If one face of a prism of prism angle 30° and $μ = \sqrt{2}$ is silvered, the incident ray retraces its initial path. What is the angle of incident?
Answer & explanation
Correct answer: option 3
As in ΔAED
$30° + 90° + ∠D = 180°$
$∠D = 60°$
Now as by construction
$∠D + ∠r = 90°$
$∠r = 90° – 60° = 30°$
Applying Snell’s law at surface AC
$\sin i = (\sqrt{2})\sin 30° = \sqrt{2} × \frac{1}{2}= \frac{1}{\sqrt{2}}$
$i = \sin^{–1} (\frac{1}{\sqrt{2}}) = 45°$