$A$ small bulb is placed at the bottom of a tank containing water to a depth of $\sqrt{7} \; m$. The refractive index of water is $\frac{4}{3}$. The area of the surface of water through which light from the bulb can emerge out is $x \,\pi \; m^{2}$. The value of $x$ is ...............

$A$ light ray traveling in a glass medium is incident on a glass-air interface at an angle of incidence $\theta$. The reflected $(R)$ and transmitted $(T)$ intensities,both as functions of $\theta$,are plotted. The correct sketch is:

If the critical angle for total internal reflection from a medium to vacuum is $30^o$,the velocity of light in the medium is

In the diagram shown,a ray of light is incident on the interface between medium $1$ and $2$ at an angle slightly greater than the critical angle. The light undergoes total internal reflection at this interface. After that,the light ray falls on the interface of medium $1$ and $3$,and again it undergoes total internal reflection. Which of the following relations should hold true?

The relation between the critical angles of water and glass is:

$A$ ray of light travelling in a transparent medium falls on a surface separating the medium from air at an angle of incidence of $45^\circ$. The ray undergoes total internal reflection. If $n$ is the refractive index of the medium with respect to air,select the possible value$(s)$ of $n$ from the following: