Refractive Index - ASTM D542
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 ASTM D542 is performed using an Abb� refractometer.
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.