Shake Hands interactive, Science Museum, London, 1992.
© Science Museum / Science & Society Picture Library
This exhibit, a black plastic bowl shiny enough to act like a mirror, creates an unusual kind of mirror image - one you can shake hands with. The image of your hand is called a REAL image - rays of light really do form the image, in about the same place as your hand. But in an ordinary flat mirror, the image appears BEHIND the mirror, and is not a real image because no light rays can actually pas through the mirror. The image is created as much by your eyes as by your mirror.