Question

Mention three applications of total internal reflection of light.

Answer 1

Hint: You can start by describing how total internal reflection is used in telecommunications using the example of optical fiber cable. Then explain why a diamond is cut at an angle of $23^\circ $ . Then explain the formation of mirages in brief.

Complete answer:
Three applications of total internal reflection of light are as follows:

A. Telecommunication services - It is used heavily by ISPs (Internet Service Providers) to provide us with internet connectivity. Originally broadband cables were used to provide internet to households and businesses, but now optical fiber cable has become more popular. It uses the concept of total internal reflection and provides up to 100 times more speed than traditional broadband connections. When you needed to upgrade your broadband connection for more data bandwidth (more data speed) you would have to upgrade the wires too, but with optical fiber cables it is theoretically possible to transfer a very large amount of data (speeds in Petabytes) on the same cables and the speed is only limited by your ISP and your data plan.

B. Cutting of diamond – When a jeweler grinds the diamond he is ensuring that he grinds the surface in such a way (at an angle of $23^\circ $ ) that the light that enters the diamond is internally reflected which makes the diamond shine. The more the shine of the diamond, the more will be its market value.

C. Formation of mirage – You may have seen in various movies that in deserts you can see the mirage of an oasis (basically a small pond in the desert). Mirages have been confusing the pedestrians of desert areas for a long time. Mirages are essentially formed when the light from an actual oasis suffers total internal reflection in air. Deserts are very hot and the air near the ground is warmer compared to the air above it. This can cause a difference in the refractive index of the warm and relatively cooler air and hence internal reflection takes place.

Note:
Other than the uses mentioned in the solution, there are various other applications. Binoculars use total internal reflection to work. Automatic windshield wipers in cars use total internal reflection to detect rain. Total internal reflection is also very useful in microscopy (called total internal reflection microscopy or TIRM)