A convex lens (or biconvex lens) is a lens with surfaces that curve outward (convex): the ends are narrow and the middle is wide. This is the most familiar form of converging lens, so called because light passing through such a lens is converged to a point. This point is called a focus. A convex lens can produce either a real or virtual image. When diverging beams are focused at a convex lens, they all come back and focus at one point.

When ray tracing by hand, three kinds of rays are drawn from an object, through the lens, and after the lens used to pinpoint focus of an image: Rays entering parallel to the axis will pass through the focal point on the image side of the lens. Light passing through the point one focal length from the lens along the axis will be refracted so that it is parallel to the axis, and light passing through the center will not be refracted at all.

See also

• Concave lens
• List of optical topics
• Optics
• M.C.Escher, Convex and Concave.

Lenses

Sammellinse | Lens (optisch) | kanta cembung | เลนส์นูน | 凸透镜