The science behind mind-boggling illusions has intrigued adults and children alike for years but now with their new book Optical Illusions, two of the foremost experts in optical art and illusions reveal how to wow your friends and family and make them gasp with wonder. Is it magic? Only you will know…
OPTICS IN A GLASS: REVERSING FISH
This illusion uses the power of light to make the impossible possible, or at least to appear that way. But what magical powers lie in a humble glass of water
1.Draw two fish on a sheet of paper and 2 colour in using contrasting colours.
2.Put a clear, empty glass with a round bottom between you and the piece of paper.
3.Partly fill the glass with water. You will see something that you might not expect. The bottom fish is now swimming in the opposite direction! So, how did this magic happen?
What’s going on?
This demonstrates a simple physics concept called ‘refraction’. Light bends when it travels through a transparent material. For example, when light rays go through a magnifying glass they bend towards the centre. Where the light rays come together is called the ‘focal point’, but beyond that focal point the image appears to reverse
because the light rays cross over and form a reversed image. This makes the fish appear to swim the other way!
HOLE IN THE HAND ILLUSION
This simple illusion will give you the impression that you can see right through parts of your body!
Hold the tube in your right hand up to your right eye
like a telescope. Now hold your open left hand, with its palm toward you and its edge against the tube, in front of your open left eye. Focus both your eyes ahead and both images will merge into one. Slide your left hand along the tube until you see a hole in the centre of your palm.
WHAT YOU NEED: A magazine or sheet of card rolled into a tube and held in place with a rubber band
What’s going on?
This effect is caused by binocular vision. Each of your eyes receives a different picture and your brain merges these together to create the hole in your hand.
Gianni A Sarcone and Marie-Jo Waeber are experts in brain training and are particularly involved in cognitive sciences. They have written numerous books on topics ranging from optical illusions to visual and critical thinking.
Optical Illusions by Gianni A Sarcone and Marie-Jo Waeber is published by The Quarto Group and available from October 19. Age 7+ HB £11.99