State-money box

Inside a cube-shaped money-box a mirror is fitted diagonally. A half of a symmetric solid shape is stuck in the middle of the mirror. In this way, an illusion that we can see the box inside through a transparent wall is created. Such a construction makes the other half of the box invisible and this is where the coin falls. The light reflected by the solid (and dispersed by its surface) is reflected by the mirror and reaches our eyes. It seems to us that the light was sent off by a real object positioned behind the mirror. We call such a 'non-existing' object an image. Since the image seems to be on the other side of the mirror we call it a virtual image.

The picture on the side demonstrates how the image is created by a plane mirror positioned at the angle of 45 degrees to the viewing plane.