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1. Refractive Index

   Linked via "Icelandic Spar"

   The Role of Polarization and Anisotropy
   In materials lacking cubic symmetry, such as birefringent crystals or stressed polymers, the refractive index is not constant in all directions. Such media possess an optical indicatrix, requiring the refractive index to be described by a second-rank tensor, $n_{ij}$. Incident light polarizing in different directions (ordinary and extraordinary rays) traverses the material at d…