The critical angle of light passing from glass to air is minimum for:

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:

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?

$A$ ray of light travels from a medium of refractive index $\mu$ to air. Its angle of incidence in the medium is $i$,measured from the normal to the boundary,and its angle of deviation is $\delta$. If $\delta$ is plotted against $i$,which of the following best represents the resulting curve?

$A$ cut diamond sparkles because of its

Assertion: Optical fibres are used for telecommunication.
Reason: Optical fibres are based on the phenomenon of total internal reflection.