What you need:
A coin
Glass Water
A saucer
What to do:
1. Place the coin on a flat surface such as a table.
2. Place the glass right over the coin.
3. Cover the mouth of the glass with the saucer and peek in through the sides of the glass. The coin should still be
4. Now, remove the saucer and fill the glass with water. Cover the visible. mouth with the saucer once more.
5. Look in through the sides of the glass.
What happens:
The coin has disappeared!
If you remove the saucer and look through the top of the glass, the coin’s still there.
Why?
This happens because of a special property of light known as refraction. Refraction is nothing but the bending of light as it travels from one medium to another. This is different from reflection where light simply bounces back when it hits an obstacle.
Refraction occurs because the molecules of a medium are usually packed closer together than the molecules of plain old air. So the light is unable stick to a straight path when it enters water or glass or anything denser than air.
In this case, the light rays are bent so much as they move from the coin towards you (Metal> Glass> Water> Glass > Air) that they are unable to make it to your eyes. That is why you cannot see the coin.
Picture Credit : Google
