There are some design variations including using a concave-shaped element that’s silvered ... In photographic catadioptric lenses, the secondary mirror – which has a convex surface – also serves to ...

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 ...