focal length

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:
1745–55

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Collins
World English Dictionary
focal length or focal distance
 
n
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
 
focal distance or focal distance
 
n

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

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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American Heritage
Science Dictionary
focal length   (fō'kəl)  Pronunciation Key 
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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American Heritage
Cultural Dictionary

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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