Examples from the Web for plano-concave
The achromatic lens consists of a double convex lens of crown glass combined with a plano-concave lens of flint glass.Physics|Willis Eugene Tower
Plano-concave and double concave lenses produced similar effects.Biographies of Distinguished Scientific Men|Francois Arago
The chromatic combination consists of a convex lens of crown backed by a concave, or plano-concave, lens of flint.Pleasures of the telescope|Garrett Serviss
If one of the radii becomes infinite, the lens is plano-concave (fig. 9, 5).