A lens is a transmissive optic device which focuses or disperses a light ray by means of a refraction.

 A simple lens consists of a single piece of a transparent material,

 while the emulsion lens consists of several simple lenses (rudiments),

 generally arranged along a common axis. Lenses are made from accouterments similar as glass or plastic,

 and are base and polished or moldered to an ask shape. 

A lens can concentrate light to form an image, unlike a prism,

 which refracts light without fastening.

 Bias that also concentrates or disperses to swell and radiation other than visible light are also called lenses, 

similar as fryer lenses, electron lenses, aural lenses,

 or explosive lenses. are used in colorful imaging bias like telescopes, 

binoculars and cameras.

 They're also to use as visual aids in spectacles to correct blights of vision similar as diplopia and presbyopia.