$A$ small coin is resting on the bottom of a beaker filled with liquid. $A$ ray of light from the coin travels up to the surface of the liquid and moves along its surface. How fast is the light travelling in the liquid?

$A$ large glass slab $(\mu = 5/3)$ of thickness $8 \text{ cm}$ is placed over a point source of light on a plane surface. It is observed that light emerges from the top surface of the slab through a circular area of radius $R \text{ cm}$. What is the value of $R$?

The refractive index of glass is $1.5$ and that of water is $1.33$. The critical angle for a ray of light going from glass to water is

If a ray of light in a denser medium strikes a rarer medium at an angle of incidence $i$,the angles of reflection and refraction are $r$ and $r^{\prime}$ respectively. If the reflected and refracted rays are at right angles to each other,the critical angle for the given pair of media is

Glass has a refractive index $\mu$ with respect to air,and the critical angle for a ray of light going from glass to air is $\theta$. If a ray of light is incident from air on the glass with an angle of incidence $\theta$,the corresponding angle of refraction is:

On a bright sunny day,a diver of height $h$ stands at the bottom of a lake of depth $H$. Looking upward,he can see objects outside the lake in a circular region of radius $R$. Beyond this circle,he sees the images of objects lying on the floor of the lake. If the refractive index of water is $4/3$,then the value of $R$ is: