In what ways optic fiber plays an important role in medicine?

The diagram below shows a light source P embedded in a rectangular glass block ABCD of critical angle 42°. Complete the path of the ray PQ till it emerges out of the block. Write necessary angles.
 

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

The critical angle for glass is $45°$  for the light of yellow colour. State whether it will be less than equal to or more than $45°$ for:
a. Red light
b. Blue light

In the given diagram a source of light $\mathrm{S}$ is placed at the bottom of a beaker containing water. Complete the diagram. (Critical angle for water to air is $48°$)

A swimmer inside water looks up at the sky through the surface of water. The sky is bright due to daylight. He can see:

The velocity of light in transparent media $A$ and $B$ separated by a plane boundary are $2.0\times {10}^8$ and $2.5\times {10}^8{\mathrm{ms}}^{-1}$ respectively. The critical angle for a light ray passing from $A$ to $B$ at the boundary is:

A ray of light travelling in a transparent medium of refractive index $n$ falls, on a surface separating the medium from air at an angle of incidence of ${45}^{\circ }$. The ray can undergo total internal reflection for which of the following $n$?