Lenses are used in cameras, telescopes, binoculars, microscopes and corrective glasses. A lens can be converging (convex) or diverging (concave).

Shanghai Optics Inc - Plano Concave LensesA plano concave lens is an optical lens with one concave surface and one flat surface. It has a negative focal length, and can be used for light projection, ...

Plano concave lens bend parallel input rays so they diverge from one another on the output side of the lens and hence have a negative focal length. The spherical aberration of the plano concave lenses ...

Source: NOVA: "Galileo's Battle for the Heavens" This resource was adapted from NOVA: "Galileo's Battle for the Heavens." As early as the 1300s, eyeglasses made from convex, or outward-curving ...

The lens is produced by blocky, S-shaped “unit cells” a few millimeters wide that refract radio waves in particular directions. The roughly concave lens is formed from 4,000 of these cells.

So, the glasses lens, the cornea and the eye’s lens work together to bend the light just right. A glasses lens can curve inward–called concave – to fix near-sightedness.