Light is something that we take for granted. The sun is the chief source of light. It is light that enables us to see reflections in mirrors.

Light travels in rays that move in a straight line at great speed. A light ray travels through space at 186,000 miles (297,600 km) per second! To get a good idea of what this speed means, consider that the sun is 93,000,000 miles (148,800,000 km) away from us. Light travels from the sun to the earth in just about eight minutes.

Even though light rays travel in straight lines, these rays can be bent or refracted. When light enters water or passes through glass the light ray bends at an angle. Once it leaves the glass or water the ray again moves in a straight line. However, it is traveling at a different angle than before it encountered the glass or the water.

Light is that it is related to heat. It is the sun's heat that causes it to give off light. A burning fire also creates light. If you hold your hand near, but not touching an electric light bulb you will feel the heat it gives off.

Heat can also cause light. It is heating of the filament that causes a electric bulb to glow.

When things are heated enough, they change. Vegetables become tender from cooking. A room gets warm when the furnace is switched on. Heat melts ice and boils water.

Here is an interesting experiment related to light!

Breaking Up Rays of Sunlight

It’s possible to break up or separate the Sun’s rays. When this is done, a ray of light suddenly shows a rainbow of colours. And you can do it in about two minutes.

You need: A baking pan or soup bowl, water, a small mirror and a sheet of white paper.

What to do: Run about an inch of water into the baking pan or soup bowl. Place a prism in this bowl/pan. Take a hand mirror, once that fits in a small purse. This mirror will help the water break up the light rays into bands of colour, just as a prism does. Set the water where sunlight shines directly on it, either indoors or outside. Lean the mirror against one edge of the pan or bowl. Direct the mirror’s reflection onto a white ceiling or wall or a sheet of white paper. If you are outside, you will probably need to use the paper as your viewing screen.

What happens: You will see a rainbow of colours on the ceiling or wall or sheet of paper. These colours start with red and end with violet.

Why: Water causes the rays of sunlight reflected from the mirror to bend. When light rays bend, each colour in the ray bends at a different angle. This causes rainbow effect. All the colours we normally see, such as red, orange, and yellow, green, blue and violet- are contained in sunlight. We see objects as having colour depending upon which light rays they reflect. In the case of a prism, we get to see a rainbow because all the colours are reflected.

Author: Pratikshya Dash, Class 12, Kendriya Vidyalaya No.1,OE,Trichy.