$A$ ray of light propagates from glass (refractive index $= 3/2$) to water (refractive index $= 4/3$). The value of the critical angle is:

$A$ point source of light is placed at a depth $h = 0.5 \, m$ below the surface of a liquid $(\mu = \frac{5}{4})$. Then,the fraction of light energy that escapes directly from the liquid surface is:

The reason for the shining of an air bubble in water is

Assertion: The air bubble shines in water.
Reason: Air bubble in water shines due to refraction of light.

For the given incident ray as shown in the figure,what is the minimum refractive index of the prism required for total internal reflection of this ray?

$A$ hemispherical vessel is completely filled with a liquid of refractive index $\mu$. $A$ small coin is kept at the lowest point $(O)$ of the vessel as shown in the figure. The minimum value of the refractive index of the liquid so that a person can see the coin from point $E$ (at the level of the vessel) is . . . . . . .