a. What is the principle used in optical fibres ?
b. Explain briefly the working principle.
c. What are the uses of optical fibres ?

Explanation

a. Total internal reflection
b. Optical fibres work on the principle of total internal reflection. A fibre consists of large number of very long fine quality glass or quartz ( of higher refractive index. ) they are coated with a thin layer of material of lower refractive index.
When light is incidentat a small angle on one end, it is refracted into the fibre and falls on the surface of coating . Until the angle of incidence remains greater than criticl angle of fibre, it is completed again and again. Then it emerges out through the other end even if the fibre is bent.
c. Uses
i. Used as .light pipe. in medical and optical diagnosis.
ii. Used in optical signal transmission.
iii. Used to carry telephone, television and computer signals as pulses of light.
iv used for transmission nad receiving electrcial signals which have been converted into light.