Fibre-optic cable

Do you know how the total internal reflection works? The light cannot leave water. In the same manner light can be sent in a cable.

The cable is made of glass and is very similar to the electric one. But it differs a little bit inside and on the surface. Light cannot leave the cable because of the differences in the refraction indexes ( they are greater in the cable that on its edges) and travels till the edge of the cable.

The fibre-optic cables are used in telecommunication to send information. If the cable is made of fibre it can be made into a lamp or a colourful sweeper.