The curved surfaces refract, or bend, light rays coming from an object. Cameras, telescopes, binoculars, microscopes and projectors all use lenses. Convex lenses are thicker in the middle than on the edges and cause light rays to converge or come together. Things look bigger through a convex lens. A convex lens will concentrate a beam of light on a surface causing it to appear brighter.
Convex lenses can focus light and project an image.
The point where light rays converge after passing through a lens is called the focal point. The distance from the lens to focal point is called the focal length. Concave lenses are thicker on the edges than in the middle. They cave in toward the center. Things look smaller through a concave lens.