12-23-2021, 05:30 AM
lens, in optics, piece of glass or other transparent substance that is used to form an image of an object by focusing rays of light from the object. A lens is a piece of transparent material, usually circular in shape, with two polished surfaces, either or both of which is curved and may be either convex (bulging) or concave (depressed). The curves are almost always spherical; i.e., the radius of curvature is constant. A lens has the valuable property of forming images of objects situated in front of it. Single lenses are used in eyeglasses, contact lenses, pocket magnifiers, projection condensers, signal lights, viewfinders, and on simple box cameras. More often a number of lenses made of different materials are combined together as a compound lens in a tube to permit the correction of aberrations. Compound lenses are used in such instruments as cameras, microscopes, and telescopes.
Optical principles for lenses
A optical lens produces its focusing effect because light travels more slowly in the lens than in the surrounding air, so that refraction, an abrupt bending, of a light beam occurs both where the beam enters the lens and where it emerges from the lens into the air.
depending on the focal length of the lens and on the distance between the lens and the object. The focal length of a lens is the distance from the centre of the lens to the point at which the image of a distant object is formed. A long-focus lens with beamsplitters forms a larger image of a distant object, while a short-focus lens forms a small image.
. Lenses also vary greatly in diameter, from as small as 0.16 cm (1/16 inch) for an element in a microscope objective to as large as 100 cm (40 inches) for an astronomical telescope objective. In reflectors and several other types of astronomical telescopes, concave mirrors are used for the objective instead of lenses.
Optical principles for lenses
A optical lens produces its focusing effect because light travels more slowly in the lens than in the surrounding air, so that refraction, an abrupt bending, of a light beam occurs both where the beam enters the lens and where it emerges from the lens into the air.
depending on the focal length of the lens and on the distance between the lens and the object. The focal length of a lens is the distance from the centre of the lens to the point at which the image of a distant object is formed. A long-focus lens with beamsplitters forms a larger image of a distant object, while a short-focus lens forms a small image.
. Lenses also vary greatly in diameter, from as small as 0.16 cm (1/16 inch) for an element in a microscope objective to as large as 100 cm (40 inches) for an astronomical telescope objective. In reflectors and several other types of astronomical telescopes, concave mirrors are used for the objective instead of lenses.