Oh-3 Calcite (Birefringence)
Published: Wednesday 15 March 2006 - Updated: Monday 28 March 2011
To demonstrate that an anisotropic crystal exhibits two different indices of refraction.
- Leitz polarizing apparatus
- Calcite crystal
The Leitz Projector is assembled with the object stage containing Sample 4 (Calcite with fixed pinhole stop). The polariser and analyzer are removed. The lens forms an image of the pinhole stop on the projector screen. A double image is formed due to the birefringence of the calcite. As the object stage is rotated one image remains stationary (ordinary ray) while the second image rotates around the first (extra-ordinary ray)
The light of the second image is polarised veryically to that of the extraordinary beam. This may be shown by introducing the analyser in front of the lens. As the object stage is rotated the two pinhole stop images appear twice alternately bright and dark.