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. : n

index of refraction

noun

1. another name for refractive index

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.

Word History and Origins

Origin of index of refraction¹

First recorded in 1820–30

Example Sentences

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

From Scientific American

Since the air’s index of refraction changed so dramatically in the lowest levels of the atmosphere, light that would otherwise rise was instead refracted back toward the ground.

From Washington Post

When light passes into a material of a different index of refraction, which is often proportional to the density, part of the light reflects and part of it bends.

From New York Times

In regards to the second photon, the region of the Rydberg state has a different index of refraction than the rest of the gas.

From Scientific American

But if a medium has an index of refraction that varies gradually rather than abruptly, it will make the the paths of light rays curve as they travel through it.

From Scientific American