A spyglass with a plano-convex lens that focuses at 12 inches and a plano-concave lens that focuses at four inches, he found, magnifies images three times (12 divided by four). Galileo played with ...

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.

Several other lenses are demonstrated, including a cylindrical convex lens, but these are only planoconvex lenses, or lenses that are flat on one side. Biconvex lenses can be constructed by gluing ...