Do you want to see an interesting optical illusion? If you do, put your two forefingers together and hold them 7 or 8 centimetres in front of your eyes, as shown in the picture. Look over the

AMUSING EXPERIMENTS

A FUNNY FINGER

Do you want to see an interesting optical illusion? If you do, put your two forefingers together and hold them 7 or 8 centimetres in front of your eyes, as shown in the picture. Look over the fingers and focus your eyes on something far away. Now hold your fingers a centimetre away from each other and look between them. You will see a funny finger in the air with a nail at each end!

WATERMARKS

Here is an interesting way to write a secret letter. You do it with the help of watermarks. If you collect stamps, you know what a watermark is. On every stamp there is a mark which you cannot see. You can see it only when you put the stamp in water. This mark is called a “watermark”. The watermark proves that you have a real stamp. People make watermarks on stamps by applying pressure. The places where they have applied pressure reflect light in a different way when they are wet.

SPECTRUM ON THE CEILING

One of the Newton’s most famous experiments was to pass a beam of sunlight through a prism to form rainbow colours on the wall. You can carry out an experiment of this sort with an electric torch, a mirror and a bowl of water. Put the mirror in the bowl so that it is at an angle of 30 to the level of the water. When it is dark in the room, you shine your torch on the mirror. A small spectrum of colours will appear on the ceiling.

Дата добавления: 2015-09-30