rapidity of a lens

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• Lens speed — refers to the maximum aperture diameter, or minimum f number, of a photographic lens. A lens with a larger maximum aperture (that is, a smaller minimum f number) is a fast lens because it delivers more light intensity (illuminance) to the focal… …   Wikipedia

• F-number — In optics, the f number (sometimes called focal ratio, f ratio, or relative aperture [Smith, Warren Modern Lens Design 2005 McGraw Hill] ) of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; …   Wikipedia

• speed — speedful, adj. speedfully, adv. speedfulness, n. speedingly, adv. speedingness, n. speedless, adj. /speed/, n., v., sped or speeded, speeding. n. 1. rapidity in moving, going, traveling, proceeding, or performing; swiftness; celerity: the …   Universalium

• microscope — /muy kreuh skohp /, n. 1. an optical instrument having a magnifying lens or a combination of lenses for inspecting objects too small to be seen or too small to be seen distinctly and in detail by the unaided eye. 2. (cap.) Astron. the… …   Universalium

• Circle of confusion — For the closely related topic in microscopy, see Point spread function. In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as… …   Wikipedia

• medicine, history of — Introduction  the development of the prevention and treatment of disease from prehistoric and ancient times to the 20th century. Medicine and surgery before 1800 Primitive (primitive culture) medicine and folklore       Unwritten history is not… …   Universalium

• speed — [[t]spid[/t]] n. v. sped speed•ed, speed•ing 1) rapidity in moving, traveling, performing, etc.; swiftness 2) relative rate of motion or progress: the speed of light[/ex] 3) aum a gear ratio in a motor vehicle or bicycle 4) pht a) the sensitivity …   From formal English to slang

• Fiber — The parts of plants that cannot be digested, namely complex carbohydrates. Also known as bulk or roughage. Complex carbohydrates from plants are rich in starch and fiber. Examples of plants that provide complex carbohydrates (fiber) are fresh… …   Medical dictionary

• Arthur Currie — Infobox Military Person name= Sir Arthur William Currie lived=December 5, 1875 ndash; November 30, 1933 placeofbirth=Strathroy, Ontario placeofdeath=Montreal, Quebec placeofburial=Mount Royal Cemetery Montreal, Quebec caption=General Sir Arthur… …   Wikipedia

• glass — glassless, adj. glasslike, adj. /glas, glahs/, n. 1. a hard, brittle, noncrystalline, more or less transparent substance produced by fusion, usually consisting of mutually dissolved silica and silicates that also contain soda and lime, as in the… …   Universalium

• Mirage of astronomical objects — Mock mirage of the setting sun A mirage of an astronomical object is a naturally occurring optical phenomenon, in which light rays are bent to produce distorted or multiple images of an astronomical object. The mirages might be observed for such… …   Wikipedia