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

The index of refraction outside the fiber must be smaller than inside, a condition that is easily satisfied by coating the outside of the fiber with a material having an appropriate refractive index.

From Textbooks • Aug. 12, 2015

Since the index of refraction of the lens is greater than that of air, the ray moves towards the perpendicular as it enters and away from the perpendicular as it leaves.

From Textbooks • Aug. 12, 2015

One of them obeys the ordinary law of refraction discovered by Snell, and is, therefore, called the ordinary ray: its index of refraction is 1.654.

From Six Lectures on Light Delivered In The United States In 1872-1873 by Tyndall, John