What is partial reflection of light?

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.
 

Name the physical principle on the basis of which optical fibres work.

Which of the following are technological applications of Total Internal Reflection?

$1$. Mirage

$2$. Diamond

$3$. Prism

$4$. Optical Fiber

Select the correct answer using the code given below:

White light is incident on the interface of glass and air as shown in the figure. If green light is just totally internally reflected then the emerging ray in air contains

In figure, the optical fibre is $l= 2 \mathrm{m}$ long and has a diameter of $d=20 \mathrm{\mu m}$. If a ray of light is incident on one end of the fibre at angle ${\theta }_1=40°$, the number of reflection it makes before emerging from the other end is close to : (refractive index of fibre is $1.31$ and $\sin 40°=0.64$)

Consider the following field in which photonics technology is used:

1. Electronics
2. Telecommunications
3. Health sector
4. Defense sector

Select the correct answer using the code given below:

An object is placed on the principal axis of a convex lens of focal length $10$ cm. If the distance of the object from the lens is $30$ cm, what is the distance of the image formed?