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For a typical sample of NPB the refractive index and extinction coefficient at 632.8 nm are 1.78541 and 6.422377E-09. Below are files of complete refractive index and extinction coefficients. If the file is not available for download, you can request our proprietary file by clicking "Request".
Refractive Index Reference - Filmetrics Composite
No guarantee of accuracy - use at your own risk.
Proprietary encrypted file for use with Filmetrics Systems: