Field of application:
The calcite crystal is an optically anistropic medium, which doubles the font when the crystal is placed on a text, for example. Easy to demonstrate, it shows the effect of birefringence, which is treated in school lessons.
Cause of the effect: the crystal has different refractive indices (no and ne) depending on the direction of propagation and the polarization of the light. Light beams are therefore separated into two partial beams polarized perpendicular to each other (ordinary and extraordinary beam).
Crystal: double spar (also called calcite or iceland spar; CaCO3)
Refractive indices: no: 1.658; ne: 1.486
Dimensions: approx. 22 mm x 16 mm x 12 mm (approximate data, since naturally grown crystal)