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focal length

noun, Optics.
1.
the distance from a focal point of a lens or mirror to the corresponding principal plane. Symbol: f.
2.
the distance between an object lens and its corresponding focal plane in a telescope.
Also called focal distance.
Origin
1745-1755
1745-55
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for focal length

focal length

noun
1.
the distance from the focal point of a lens or mirror to the reflecting surface of the mirror or the centre point of the lens
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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focal length in Medicine

focal length n.
The distance from the surface of a lens or mirror to its focal point. Also called focal distance, focus.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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focal length in Science
focal length
  (fō'kəl)   
The distance between the optical center of a lens or mirror to its focal point.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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focal length in Culture

focal length definition


The distance between the focal point of a lens (that is, the point at which the lens will focus parallel rays of light) and the lens itself.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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10
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