Can Light Travel Through Wires Just Like Electricity?

Your physics tuition always brings you interesting and thought provoking stories. Here is another interesting question from your physics tuition. It is well known that electricity can travel through metallic wires from one place to another. Do you know that light can also travel through wires? These wires are not metallic ones, but are made of glass. Light carrying wires are extremely thin and are called optical fibres. The branch of science dealing with the conduction of light through fibres is called fibre optics.

John Tyndall, a British physicist in 1870, showed that light can travel along a curved rod of glass or transparent plastic. Light travels through transparent rods by total internal reflection process. The sides of the fire reflect the light and keep it inside as the fibre bends and turns.

These narrow fibres contain a slender core of glass having a higher refractive index that is surrounded with another thin cladding of glass having a lower refractive index. Light is carried by the core and the covering aids in bending the light back to the core.

The fibres are drawn from thick glass rods in a special furnace. The glass rod of higher refractive index is inserted in a tubing of glass of lower refractive index. Then the two are lowered carefully and slowly through a vertical furnace and the fibre drawn from the lower end is wound on a revolving drum. With this method fibre of about 0.025 mm in diameter can be drawn.

Thus the fibres prepared in this manner, must be aligned in the proper way to form a bundle. They should never cross each other at any stage. In that case the image transported through the fibres will become scrambled. They have to be kept always in straight lines. After this aligned bundle is prepared successfully, it then can be turned or bent in any required direction.

They are many uses of fibre bundles. Physicians use instruments with fibre bundles to examine body cavities and the inner part of hollow organs by sending light from an external lamp. These instruments are known as fibre-scope. By introducing the bundle into the stomach or bladder, photographs can be made of the internal organs.

Fibre optic instruments can transmit signals like programs in television and telephonic conversations. In the future, using laser beams and single bundle of optical fibres, scientists will be able to send thousands of telephone conversations simultaneously.

We hope you enjoyed this lesson from physics tuition. We will be back with more such interesting findings in our next physics tuition.

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