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

---

index of refraction British  

noun

1. another name for refractive index

---

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.

---

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

Suppose light were incident from air onto a material that had a negative index of refraction, say –1.3; where does the refracted light ray go?

From Textbooks • Aug. 12, 2015

We know that the index of refraction n depends on the medium.

From Textbooks • Aug. 12, 2015

If balsam of copaiba is made use of, the index of refraction of which is 1.50, a symmetrical field of about 24� will be obtained.

From Scientific American Supplement, No. 441, June 14, 1884. by Various