The refractive indices of glass and water are 3/2 and 4/3, respectively. If light passes from glass to water, the critical angel is

$\sin^{-1} (8/9)$

The correct answer is Option (1) → $\sin^{-1} (8/9)$

Given:

Refractive index of glass: $n_1 = \frac{3}{2} = 1.5$

Refractive index of water: $n_2 = \frac{4}{3} \approx 1.333$

Critical angle for total internal reflection:

$\sin \theta_c = \frac{n_2}{n_1} = \frac{1.333}{1.5} \approx 0.8887$

Therefore:

$\theta_c = \arcsin(0.8887) \approx 62.7^\circ$