A very popular physics toy consists of two concave spherical mirrors facing each other like the shells of a clam. If a coin or button is placed on the surface of the lower mirror, its image appears in the hole at the center of the top mirror. The image looks so real that people will try to push the button or pick up the coin. It’s fun to watch their faces as they discover that there is actually nothing there! The separation of the mirrors in this toy has been carefully chosen so that the real image appears in the hole as if it were sitting on a clear portion of the upper mirror. The image is the same size as the object.