refractive index

American  

noun

Optics.

1. index of refraction.

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refractive index British  

noun

1.  ν.   μ.  physics a measure of the extent to which radiation is refracted on passing through the interface between two media. It is the ratio of the sine of the angle of incidence to the sine of the angle of refraction, which can be shown to be equal to the ratio of the phase speed in the first medium to that in the second. In the case of electromagnetic radiation, esp light, it is usual to give values of the absolute refractive index of a medium, that is for radiation entering the medium from free space

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Etymology

Origin of refractive index

First recorded in 1830–40

Example Sentences

The resulting patterns show strong optical contrast because of the light-induced refractive index changes, making them easy to detect with optical methods.

From Science Daily • Apr. 21, 2026

This effect, known as photorefractivity, occurs when exposure to light alters the refractive index.

From Science Daily • Apr. 21, 2026

By comparing the patterns in forward- and back-scattered light, they could estimate each particle's size and its refractive index, which describes how strongly light bends or scatters when it passes through a material.

From Science Daily • Nov. 17, 2025

This plate is almost transparent to the terahertz rays, but it has a higher refractive index than the surrounding air, so at each point of the plate, it changes the incident wave a little.

From Science Daily • Mar. 18, 2024

Lack of optical homogeneity due to varying refractive index is likely to be partially responsible.

From Visual Illusions Their Causes, Characteristics and Applications by Luckiesh, Matthew