The light emerging from the polaroid filter is vibrating in one plane. The filters are said to be in a crossed configuration. Polarized light microscopy To do polarized light microscopy one must install two polarizing filters. The first is placed in the head and the second on the lamp or in the condenser's filter holder. The latter is rotated to obtain a complete extinction of light.
Elements seen in polarized light microscopy of urine are mostly birefringent crystals.
Birefringency Birefringency is a crystal property. A light ray passing through a different phase with an angle will be deviated by a property called refraction. An isotropic body will have the same refractive index for all the direction of incident light. Many crystals are said to be anisotropic that is birefringent. The two refracted waves emerging from a birefringent crystal are called the ordinary wave and the extraordinary wave.