A plano-concave lens is a lens with one side being flat and the other side being concave. It is characterized by being thin in the center and thick at the edges, and can make parallel light rays ...

In a ray diagram, a concave lens is drawn as a vertical line with inward facing arrows to indicate the shape of the lens.

Convex and concave lenses can both be used to correct defects of vision. The most commonly occurring defects of vision are ‘short sightedness’ and ‘long sightedness’. People who are ...