Question

A ray is incident on boundary separating glass and water. Refractive index for glass is $\frac{3}{2}$ and refractive index for water is $\frac{4}{3}$ critical angle for glass-air boundary is

• A. $\sin ^{-1}\left(\frac{3}{4}\right)$
• B. $\sin ^{-1}\left(\frac{2}{3}\right)$
• C. $\sin ^{-1}\left(\frac{8}{9}\right)$
• D. $\sin ^{-1}\left(\frac{1}{9}\right)$

Answer 1

Answer: (C)

$\sin i_{C}=\frac{\mu_{r}}{\mu_{d}}$
Where $\mu_{r}=$ R.I. of rarer medium
$\mu_{d}=$ R.I. of denser medium
$\therefore \sin i_{C}=\frac{4}{3} \times \frac{2}{3} $
$ i_{C}=\sin ^{-1}\left(\frac{8}{9}\right)$