focal length
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noun Optics.
the distance from a focal point of a lens or mirror to the corresponding principal plane. Symbol: f
the distance between an object lens and its corresponding focal plane in a telescope.
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Question 1 of 7
Let’s start with some etymology: What are the origins of the typographical word “bracket”?
First appeared around 1750, and is related to the French word “braguette” for the name of codpiece armor.
First appeared in 1610, based on the French word “baguette” for the long loaf of bread.
First appeared in 1555, and is related to the French word “raquette” for a netted bat.
TAKE THE QUIZ TO FIND OUT Also called focal distance.
Origin of focal length
First recorded in 1745–55
Words nearby focal length
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021
Example sentences from the Web for focal length
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British Dictionary definitions for focal length
focal length
focal distance
noun
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
Medical definitions for focal length
focal length
n.
The distance from the surface of a lens or mirror to its focal point.focal distance focus
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Scientific definitions for focal length
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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural definitions for focal length
focal length
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 New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.