Its eye-piece has a 20 mm focal length. Find the distance between the objective lens and the eye-piece. Binoculars Binoculars are twin telescopes. Wolter grazing incidence with concentric conical surfaces having a single common point. Microscopes Microscopes are almost the same as Keplerian telescopes, except the focal lengths are in the opposite ratio.
Keplerian telescopes have a long focal length objective and a shorter focal length eye-piece.
Microscopes have a short focal length objective and a longer focal length eye-piece. Microscopes are set up to produce a final image at the distance of most distinct vision, which is about 250mm. A microscope has an objective focal length of 3mm and an eye-piece with focal length 12mm. The object is 3.5mm in front of the objective and the distance between the lenses is 33.5mm. Some microscope images of a feather.