Science Projects And Inventions

YOU NEED:

• A soft pencil
• A sheet of paper
• A piece of tape
• A glass of water

Firstly rub a soft pencil point back and forth to create a black area of graphite. Rub your thumb over the spot so that you have graphite on your thumb. Now press the tip of your thumb against the sticky side of the cellophane tape. Hold the tape up to the light to see a clear thumb print.

Secondly put a full glass of water on a table. When the water settles down, press a thumb firmly against the side of the glass which is nearer to you. Now bend your head till you can view the tip of the thumb through the water. The ridges of the thumb will be clearly visible.

HOW DOES IT WORK?

A thumb print comprises of tiny ridges. The cellophane tape picks up the ridges on its sticky end more easily than the valleys between them. It is the same with the moist side of the glass.