Category Science

You can talk on the phone to someone who is far away. You can press a button and see a television show from another country. These sounds and pictures may be travelling to you in the form of light.

Fibre-optic cables make this possible. These cables are made from clear glass or plastic strands – sometimes as thin as a human hair. These strands or fibres are gathered into bundles and wrapped in a special covering. Light travels very fast through each one of these strands. And the light can carry messages faster and more clearly than old-fashioned copper wires.

Here is how a phone call in a fibre-optic system works. When you talk to a friend, the phone changes the sound of your voice into electric signals. Then a laser at one end of the fibre changes these electric signals into high-speed flashes of light. At the other end of the fibre, a special device changes the flashes back into electric signals. Your friend’s phone then changes these signals back into the sound of your voice.

Ouch! You went swimming all day and forgot to put on more sunscreen after you got out of the water. Now you have stinging sunburn. How did you get it? Your sunburn came from light, but not from light that you can see.

When all the colours in sunlight are separated, they make a rainbow. The rainbow has a band of red on one edge and a band of violet on the other edge. In between are all the other colours. But beyond the red edge and the violet edge, there are “colours” you do not see.

A suntan or painful sunburn both come from ultraviolet rays. Ultraviolet means “beyond violet”. Ultraviolet rays are just beyond the violet edge of the rainbow. You cannot see these rays. But when your skin gets tanned or burns, you see what ultraviolet energy can do.

The heat you feel when the sun is bright comes from infrared rays. Infrared means “below red”. Infrared rays are just below the red edge of the rainbow. Like ultraviolet rays, these rays can’t be seen either. But you can feel them. When they hit something, the energy they give off makes that object heat up. Pavements get hot in summer because they absorb energy from the sun’s infrared rays.

Think of sunsets and traffic lights, campfires and television screens. They all give off light in many colours.

All the colours of light are given off in the same way. When atoms are heated, they soak up energy. Then they give off the energy as bundles of light.

All light comes from atoms. It is produced by atoms that have gained energy. For example, atoms take up energy when they are heated. Then they give up energy in the form of light.

This light may have a lot of energy, or just a little. The colour of the light depends on the amount of energy it has. In the visible spectrum, red light has the least energy. After red, comes orange, yellow, green, and blue. Violet light has the most energy in the visible spectrum.

In the visible spectrum, blue light has more energy than every colour except violet.

Part of the energy stored in wood is given off as light when the wood is burned.

The cheese in your sandwich is orange. The tomato is bright red. The lettuce is green. The light brown bread has a dark brown crust.

We see colours in things because of the way they reflect light. But the colours are really in the light. The light from the sun is a mixture of all colours. We call this type of light white light.

You can see these colours if you shine bright sunlight through a special glass called a prism. When white light goes through a prism, it spreads and separates into a band of colours, like a rainbow. It has six bands of colour – violet, blue, green, yellow, orange, and red.

When white light shines on something, that object absorbs, or soaks up, some of these colours. But it reflects other colours. Objects appear to be the colours they reflect. So the tomato in your sandwich looks red because it reflects red and absorbs other colours. Lettuce reflects green. Black objects absorb nearly all the light that reaches them. So you don’t see any colour in something that is black.

Picture Credit : Google

There you are with that teddy bear you had when you were 2 years old. Someone took your picture. The camera “captured” your image.

To make a photograph, you look through a tiny window called a viewfinder to see what will be in the picture. Next, you press a button that controls a small opening called a shutter. Most of the time, the shutter is closed. When you take a picture, the shutter opens for just a small part of a second.

Behind the shutter is a lens, which bends light rays and makes them focus, or come together. The light is captured on film, or if you are using a digital camera, on an electronic chip. The light “prints” a picture on the film or chip.

When you use up a roll of film, you take it to a store to be developed. Then you will have pictures you can keep.

A digital camera stores your photographs on the electronic chip. You can view pictures from a digital camera on a computer or television screen. You can use your computer to send the pictures to your friends, or you can print them out.