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index of refraction

noun Optics.
  1. a number indicating the speed of light in a given medium as either the ratio of the speed of light in a vacuum to that in the given medium (absolute index of refraction) or the ratio of the speed of light in a specified medium to that in the given medium (relative index of refraction). Symbol: n
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Origin of index of refraction

First recorded in 1820–30
Also called index, refractive index.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for index of refraction

Historical Examples

  • He'd gotten an index-of-refraction reading on crystals too small to be seen except through a microscope.

    The Hate Disease

    William Fitzgerald Jenkins


British Dictionary definitions for index of refraction

index of refraction

noun
  1. another name for refractive index
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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

index of refraction in Science

index of refraction

  1. A measure of the extent to which a substance slows down light waves passing through it. The index of refraction of a substance is equal to the ratio of the velocity of light in a vacuum to its speed in that substance. Its value determines the extent to which light is refracted when entering or leaving the substance.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.