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Optical instrument for providing a magnified view of distant objects, consisting of two similar telescopes, one for each eye, mounted on a single frame. In most binoculars, each telescope has two prisms, which reinvert the inverted image provided by the eyepiece of each telescope. Light rays travel along a folded path inside the telescopes, so the instrument has a shorter overall length. The prisms also provide better depth perception at greater distances, by allowing the two objectives (object lenses) to be set farther apart than the eyepieces. Binocular eyepieces are often fitted to microscopes or other optical instruments.
This entry comes from Encyclopædia Britannica Concise. For the full entry on binoculars, visit Britannica.com.