Wondering if computer glasses really help An expert explains how they reduce eye muscle work by 50 ease strain and improve ...

That secondary mirror, in turn, bounced the light (and thus the image seen) into a convex ... in the objective lens, they could cause the red and blue ends of the spectrum to converge towards ...

A lens is a specially shaped pieces of glass or transparent plastic, that is used to focus light. A convex lens is made from a transparent material that bulges outwards in the middle on both sides.