lens. 1

A piece of gla or other transparent substance so curved on one or more of its surfaces as to refract rays 483 of light, either dispersing or converging them or rendering them parallel. 2. See crystalline I. achromatic 1., apochromatic 1. A 1. so constructed as to correct the aberration of refrangibility, or chromatic aberration, of common l'es. bicylindrical l'cs. L'es which have two cylindrical curved surfaces the axes of which are at right angles to each other, bifocal l'es. L'es in which the upper half is so ground as to be suitable for distant objects, and the lower half so ground as to be suitable for near objects, concave cylindrical 1. A 1. the surface of which represents the concave or inner surface of a cylindrical tube, concave 1. See double concave I., planoconcave I., and convexoconcave I. concavoconvex 1. A 1. with one surface convex and the other concave, the curvature of the former being the greater. convergent 1., converging 1. A 1., double convex, planoconvex, or concavoconvex, such as causes the rays to converge to a focus, convex cylindrical 1. A 1. the surface of which represents the convex or outer surface of a cylindrical tube, convexoconcave 1. A 1. with one surface convex and the other concave, the curvature of the latter being the greater, crystalline 1. A biconvex transparent body, lying in its capsule behind the pupil of the eye and maintained in place by its suspensory ligament. It is made of long nucleated and prismatic fibers, with serrated edges, so arranged as to divide the ma into sectors. The 1. is also divisible into concentric lamellae. It serves to refract the rays of light entering the pupil and impinging on its surface so as to bring them to a focus upon the retina, cylindrical 1. See concave cylindrical I. and convex cylindrical I. double concave 1. A 1. both faces of which are concave. double convex 1. A 1. both faces of which are convex, oil immersion 1. See under immersion, planoconcave 1. A 1. one face of which is plane and the other concave, planoconvex 1. A 1. one face of which is plane and the other convex, plus 1., positive 1. A convex or magnifying 1. trial 1. A 1. employed in testing the refraction of the eye. [Lat., lens, a lentil.]