Science Projects And Inventions

YOU NEED:

• A white wall

Stare at the centre of the picture in the illustration even as you count slowly till 100. Now look aside and stare at a white wall.  What you will see is a startling image of a young boy playing with a steam engine. The apparition that you have just seen is known as an afterimage. The retina in your eye tires of seeing black and white, and for a few moments when you look at the wall, it reverses black and white. If you happen to stare at a colour picture, its afterimage will change the colours to their complements. If you stare at a red apple for a minute or two, lo you will catch a glimpse of a green apple on the white wall. Gaze at an orange, and there will be a blue one on the wall.