Concave Lenses are used in the treatment of myopia or shortsight.
Rayleigh points out that this clinging of the sound to the surface of a concave wall does not depend on the exactness of the spherical form.
He refers to Maurolycus' work with concave specula.
3) the terms by which these parts are designated: The skin does not form eyelids; but the epidermis passes over the eye, forming a transparent disk, concave like the glass of a watch, behind which the eye moves.
The arches bear on the convex outer side the delicate arborescent gills, and on the concave inner side develop a membranous septum with vermicular perforations, a special sifting or filtering contrivance through which the water absorbed by the mouth has to pass before reaching the respiratory organs of the branchial apparatus.