You can perform quite a number of curious experiments by the agency of reflections. In fact, many of the optical illusions seen on the stage are the result of misleading reflections. Here is one item that will be certain to mystify a good many of your friends. Construct a cardboard box that is a perfect cube. A 6 inch side will be convenient for the purpose. Arrange the lid so that it has a tuck-in flap to keep out the light. In one of the sides, cut out a circle of 4 inches diameter. Lastly, paint the whole of the inside black.
For the experiment, you will want a piece of clear glass which can be wedged into the box diagonally that is, from once corner to the opposite corner and, of course, it must be 6 inches high. When you are ready, stand the glass diagonally across the box, dividing it into two compartments. In one compartment, in the corner away from the glass partition, stand a tumbler or a bottle full of water, and in the opposite corner, in the other compartment, stand a small ornament of man, a doll, or even a card cut out to look like one, provided the figure is smaller than the tumbler or bottle.
Look through the circular opening and the man will appear to be imprisoned in the vessel. If he is not quite standing in the water, a little alteration in the vessel. If he is not quite standing in the water, a little alteration of his position will quickly put him right. Then let your friends look through the opening. They will be mystified.