Refractive Index

معامل الانكسار

Refractive index, also called index of refraction, measure of the bending of a ray of light when passing from one medium into another. If I is the angle of incidence of a ray in vacuum (angle between the incoming ray and the perpendicular to the surface) and r is the angle of refraction (angle between the ray in the medium and the perpendicular), the refractive index n is given by the ratio of the sine of the angle of incidence to the sine of the angle of refraction: n = \sin I / \sin r. Refractive index is also equal to the velocity of light c of a given wavelength in empty space divided by its velocity v in a substance, or n = c/v.

Quick Decode

Refractive index describes how slowly light travels in a material compared with a vacuum: n = c/v. A difference in refractive index between two materials helps determine how much light changes direction when it crosses their boundary, which is important for focusing light in the eye and in spectacle lenses.

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References (1)
  1. Britannica Editors. (2026, August 11). Refractive index. Encyclopædia Britannica. Retrieved September 30, 2026, from https://www.britannica.com/science/refractive-index