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Refractive Index - ISO 489

Refractive index, or index of refraction, is the ratio of the velocity of light in a vacuum to its velocity in the material in question. Refractive index is useful for identifying materials, and is important in optical applications.
Testing for ISO 489 is performed using one of two test methods as described below.

Refractive Index Testing Methods
Method Name Description
A Refractometric Method Measurements are made using an Abbe refractometer. This method is recommended when high accuracy is required.
B Immersion Method Measurements are made using a microscope by utilizing the Becke line phenomenon. Accuracy is similar to that of Method A.

Index of refraction can be calculated using Snell's Law:
n1 / n2 = sin θ2 / sin θ1
where n1 and n2 are the refractive indices of mediums 1 and 2, θ1 is the angle of incidence, and θ2 is the angle of refraction.

Refractive Index Geometry

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