The compound microscope uses two (or more) lenses to increase the size of the image focused on the viewer's retina. Light rays (A) travelling outward from an object (B) bend as they pass through the first lens (C). The rays converge at a focal point (D). The rays cross and spread out until they create an image known as the first image (E). The light rays making up this enlarged image are allowed to spread out further before they are bent inward by a second lens (F), the eye-lens. The rays passing through the eye-lens enter the eye at an angle, so they appear to be coming from a much larger object (G), the virtual or final image.Courtesy of Lucent Books Inc.