Birefringence is the optical phenomenon where a single light ray splits into two rays when it passes through an anisotropic material.
Key Features:
- The two rays are:
- Ordinary ray (O-ray): Obeys Snell’s law.
- Extraordinary ray (E-ray): Deviates from Snell’s law.
- Both rays are polarized perpendicular to each other.
- The phenomenon arises due to:
- Different refractive indices for different polarization directions.
- Anisotropy in the crystal structure.
Materials Showing Birefringence:
- Calcite
- Quartz
- Mica
- Some plastics under stress
Applications:
- Optical mineralogy
- Polarized microscopes
- Stress analysis in materials
- Liquid crystal displays (LCDs)
- Used in birefringent filters and wave plates in optics
Important Concept:
- Birefringence occurs only in anisotropic materials – not in isotropic materials like glass or water.
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