Paragraph on “Where does Light come from?” complete paragraph for Class 9, Class 10, Class 11 and Class 12

Where does Light come from?

Natural light comes mostly from the sun. The sun is a huge ball of fiery gas and is tremendously hot. Light from the sun reaches us during the day when we are on the side of the Earth turned towards it. The first men de-pended on the sun and could only see well during the day. The only way they had of making light was fire.

Thousands of years ago simple oil lamps were invented. These have a ‘wick’, usually a piece of cotton, to soak up oil from a little jar. When the top of the wick is lit the oil burns with a clear flame. In candles, the wick runs down the middle of a stick of wax. The flame melts the wax which then soaks the wick as oil does, and burns. Gas lamps were invented much later. In these an inflammable gas burns as it comes out of a jet. There is a special `mantle’, like a very fine net, around the gas flame. This mantle glows as it gets hot and gives off much more light than the flame alone.

Nowadays most lights are powered by electricity. The ordinary light-bulb has a very thin wire inside called a ‘filament’. Electricity flows through this and heats it up so that it gives out a bright light. The filament is so hot that it would burn if there were air round it. Instead the bulb is filled with a  gas in which nothing will burn. Many street lamps give out a different kind of electric light. In this electricity is passed through a gas and the gas itself glows brightly. One gas often used for this is called ‘sodium vapour’ and give a yellow light.