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Technical Glossary Refractive Index

[Refractive Index]

When light enters a material, its speed changes. The refractive index is unique to each substance and describes the difference between the speed of light within a material and the speed of light in a vacuum. It expresses the difficulty which light experiences when moving through a substance. Thus, the higher a substance’s refractive index, the slower light travels through it. The refractive index for a substance differs according to the wavelength of light used. However, it is custom to use light of wavelength 589.3 nm (the sodium D line) when evaluating.
Below is a list of the refractive indices of several common substances.

Material Refractive Index Notes
Air 1.000292 0、1 atmosphere
Carbon dioxide 1.00045
Ice 1.309 0
Water 1.3334 20
Ethanol 1.3618
Paraffin 1.48
Polymethylmethacrylate 1.491 20
Quartz crystal 1.5443 18
Optical glass 1.43-2.14
Sapphire 1.762-1.770
Diamond 2.417
Silicone rubber 1.40-1.43
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