Focal may refer to: Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ...
Focal (lexicographical website), an Irish lexicographical website
focal. ... FOCAL, (abbreviation of FOrmula CALculator), is an interpreted programming language resembling JOSS. Largely the creation of Richard Merrill, FOCAL was initially written for and had its largest impact on the Digital Equipment Corporations (DECs) PDP-8 computers. ... FOCAL-69 was the landmark version of the FOCAL programming language, more widely publicized than the original version of the language created in 1968. ... The Forty-One Calculator Language (Focal) is the language used to program the HP-41 range of calculators from Hewlett-Packard. ... Look up focus in Wiktionary, the free dictionary. ...
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A focal point may mean: Focus (optics), the point at which initially collimated rays of light meet after passing through a convex lens, or reflecting off of a concave mirror. ... Immunofluorescence coloration of actin (green) and the focal adhesion protein vinculin (red) in a fibroblast. ... In literature, a focal character is the character around whom the events of the story revolve. ... Focal dystonia is a neurological condition affecting a muscle or muscles in a part of the body causing an undesirable muscular contraction or twisting. ... A focal infection is a local infection (affecting a small area of the body) that causes subsequent infection or symptoms in other parts of the body. ... This article is about focal length related to lenses and systems of lenses. ... Focal seizures (also called partial seizures) are seizures which are characterized by: preserved consciousness in simple focal seizures impaired consciousness (dream-like) in complex focal seizures experience of unusual feelings or sensations sudden and inexplainable feelings of joy, anger, sadness, or nausea altered sense of hearing, smelling, tasting, seeing, or... For a surface in three dimension the focal surface, surface of centers or evolute is formed by taking the centers of the two circles whose radii correspond to the principal curvatures. ... Image File history File links Disambig_gray. ...
Most manufacturers specify the focal length of their various instruments; but, if it is unknown and you know the focal ratio you can use the following formula to calculate it: focal length is the aperture (in mm) times the focal ratio.
This is the ratio of the focal length of the telescope to its aperture.
The faster the focal ratio, the more coma that will be seen near the edge although the center of the field (approximately a circle, which in mm is the square of the focal ratio) will still be coma-free in well-designed and manufactured instruments.
The focal length of a lens is the distance along the optical axis from the lens to the focus (or focal point).
For a diverging lens (e.g., a concave lens), the focal length is negative, and is the distance from the lens to the point at which a collimated beam appears to be emerging from after passing through the lens.
For a spherically curved mirror, the focal length is equal to half the radius of curvature of the mirror.
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