Index of Refraction Calculator
Calculate the index of refraction of a material using Snell’s law from the angles of incidence and refraction.
What the index of refraction is
The index of refraction (refractive index) of a material describes how much light slows down and bends when passing into it, compared to its speed in a vacuum. Higher values mean light bends more and travels slower in that material.
The formula used
This calculator uses Snell’s law, n1·sin(θ1) = n2·sin(θ2), rearranged to solve for the second medium’s refractive index: n2 = n1·sin(θ1)/sin(θ2), where θ1 is the angle of incidence and θ2 is the angle of refraction, both measured from the normal to the surface. The speed of light in the medium is then found from c/n2.
This calculator assumes light of a single wavelength (refractive index varies slightly with wavelength, an effect called dispersion) and measurement of angles from the surface normal, not the surface itself. For general physics education purposes.