A biconvex<unk> <unk> es can be used to focus light A<unk>  is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple<unk>  consists of a single piece of transparent material, while a compound<unk>  consists of several simple<unk> es (elements), usually arranged along a common axis.<unk> es are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A<unk>  can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called<unk> es, such as microwave<unk> es, electron<unk> es, acoustic<unk> es, or explosive<unk> es.<unk> es are used in various imaging devices like telescopes, binoculars and cameras. They are also used as visual aids in glasses to correct defects of vision such as myopia and hypermetropia.
Lens
Eye
Globe 
Optician
DermAtlas
Pituitary gland
Heart
Optic stalk