Cambridge Encyclopedia » Cambridge Encyclopedia Vol. 45


optical light

A transparent optical element comprising two refracting surfaces, at least one of which is curved; parallel light rays passing through the lens may converge (and focus at a point) or diverge, depending on the lens shape. Lenses are characterized by their focal length (the distance at which the image of a distant object is most sharply defined) and their aperture or f-number (the light transmission). They are widely used in optical instruments, binoculars, projectors, and cameras, and are usually made of glass, sometimes of plastic.

User Comments

Your email address will be altered so spam harvesting bots can't read it easily.
Hide my email completely instead?

Cancel or