$A$ ray of light is incident on one face of a $90^{\circ}$ prism and undergoes total internal reflection at the glass-air interface. If the angle of incidence is $45^{\circ}$,then the refractive index $n$ is:

Light is incident normally on face $AB$ of a prism as shown in the figure. $A$ liquid of refractive index $\mu$ is placed on face $AC$ of the prism. The prism is made of glass of refractive index $\frac{3}{2}$. The limit of $\mu$ for which total internal reflection takes place on face $AC$ is

$A$ point source of light is placed at a distance $h$ below the surface of a large deep lake. What is the percentage of light energy that escapes directly from the water surface if the refractive index $\mu$ of the water is $4/3$ (in $\%$)? (Neglect partial reflection)

$A$ ray of light travels from a denser medium to a rarer medium. The reflected and the refracted rays are perpendicular to each other. If '$i$' and '$r_1$' are the angle of incidence and angle of refraction respectively and '$C$' is the critical angle,then the angle of incidence is

$A$ ray of light incident normally on an isosceles right-angled prism travels as shown in the figure. The least value of the refractive index of the prism must be

$A$ 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 . . . . . . .