Now a days optical fibers are extensively used for transmitting audio and video signals through long distances. The optical fibers work on

Total internal reflection

Optical fibres work on the principle of total internal reflection(T.I.R).Total internal reflection is a complete reflection of a ray of light within a medium such as optical fibre from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle.