concave lens n.
A lens having at least one surface curved like the inner surface of a sphere.
By means of a concave lens (L) the image may be made to fall on the retina (dotted lines).
It is a simple matter to counteract the effects of undue convexity by means of a concave lens.
The image formed by a concave mirror is magnified by a microscope, in the same manner as when formed by the concave lens.
Both mirrors are usually concave; if plane, a concave lens is placed immediately before them.
In the opera glass this is a concave lens while in the other it is a convex lens.
A concave lens, as might be expected, produces exactly the contrary effect on light to that of a concave mirror.
It was a concave lens, like some powerful optical instrument.
When a lens is thicker at the middle than at the sides it is called a convex lens; when thinner, a concave lens.
The form of spectroscope mentioned above, in which the collimator and slit are replaced by a concave lens, will be tried.
The opera glass consists of a convex lens as objective and a concave lens as an eyepiece.