80. Real and Virtual Image Illusions

Real: The "UFO shaped Optical Illusion" produces a stunningly real looking 3D image of a small object placed inside it. A laser can be shined right on the image, demonstrating optical reciprocity. The device consists of two parabolic mirrors, each at the focus of the other. The object is placed on the lower mirror at the focus of the upper mirror. Beams from the object diverge to the upper mirror and are reflected parallel down to the lower mirror, whence they are converged up through a hole in the upper mirror to form the image.

Virtual: In this impressive demonstration the virtual image of the flame of a concealed candle in a sheet of plate glass appears over an unlit candle wick. You can put your finger in the "flame" and grimace, or pour water over it and not put it out

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