index of refraction

American  

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. n

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index of refraction British  

noun

1. another name for refractive index

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index of refraction Scientific  

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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Etymology

Origin of index of refraction

First recorded in 1820–30

Example Sentences

Light entering a medium with a negative index of refraction, on the contrary, would bend backward, creating unexpected optical effects, such as a straw appearing to lean the wrong way.

From Scientific American • Nov. 18, 2022

The difference in index of refraction between the two materials defines the angle of that bending.

From Scientific American • Nov. 18, 2022

There is no total reflection for rays going in the other direction—for example, from air to water—since the condition that the second medium must have a smaller index of refraction is not satisfied.

From Textbooks • Aug. 12, 2015

Fibers in bundles are surrounded by a cladding material that has a lower index of refraction than the core.

From Textbooks • Aug. 12, 2015

A glass rod is visible in air or in water, but it is almost invisible in a mixture of benzol and bisulphuret of carbon, which has the same mean index of refraction as the glass.

From Popular scientific lectures by Mach, Ernst