Lenses

A lens is a transmissive optical tool that employs refraction to focus or disperse a light beam. A compound lens is made up of multiple simple lenses (elements), typically aligned along a common axis, as opposed to a simple lens, which is one solid piece of transparent material. Glass or plastic are used to make lenses, which are then polished or molded into the required shape. In contrast to a prism, which just refracts light without focusing it, a lens can focus light to create an image. Lenses are also devices that focus or disperse waves and radiation other than visible light, such as explosive lenses, microwave lenses, electron lenses, and acoustic lenses.