We are familiar with instruments that enlarge or reduce the observed size of objects. A
magnifying glass, a telescope, and a movie projector are familiar examples of instruments that enlarge the observed size of an object. Scale drawings, maps, and architectural plans are examples of images that are obtained by shrinking the observed size of an object. What all these instruments and situations have in common is that the enlarged or shrunken image maintains the same shape as the original object, but not necessarily the same size.