ABSTRACT
The difference in the refractive indices of a birefringent substance for two linearly polarized monochromatic waves propagating in a given direction is related to the difference in the absorption coefficients for the two waves. When the polarizer is rotated in its own plane, the light intensity transmitted by the combination varies; it passes through two extreme values when the transmission direction of the polarizer is parallel and perpendicular to the optical axis. In white light, the dichroism manifests itself either by a difference in the intensity of the coloured light passing through the plate, or by a difference in its coloration. Polarizing sheets are fabricated either by aligning coloured, strongly anisotropic molecules included in colourless crystals, or by dyeing with iodine long-chain molecules of plastic which have been aligned by lamination.
