Two transparent media $A$ and $B$ are separated by a plane boundary. The speed of light in those media are $1.5 \times 10^{8} \ m/s$ and $2.0 \times 10^{8} \ m/s$,respectively. The critical angle for a ray of light for these two media 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:

$A$ light ray from air is incident (as shown in the figure) on the lateral surface of a glass fiber (refractive index $\mu = 1.5$) at an angle of incidence of $60^o$, such that it undergoes total internal reflection. How much time would it take for the light to traverse the straight fiber of length $L = 1 \ km$ (in $\mu s$)?

Total internal reflection of a ray of light is possible when the ($i_c$ = critical angle,$i$ = angle of incidence)

$A$ ray of light incident on a glass sphere (refractive index $\sqrt{3}$) suffers total internal reflection before emerging out exactly parallel to the incident ray. The angle of incidence was (in $^{\circ}$)

It is found that all electromagnetic signals sent from $A$ towards $B$ reach point $C$. The speed of electromagnetic signals in glass can not be