Binoculars..How they work

Binoculars are essentially a pair of identical refracting telescopes; they have a large objective lens at the front and a number of smaller lenses to enable an image to be brought into sharp focus.
Prisms are used so that larger objective lenses can be used - otherwise they would be limited by the distance between the eyes. The prisms reflect the image through two right angles in the binoculars. The prisms also reverse the inversion that occurs in refracting telescopes.