Birefringence is a phenomenon in which light waves travel at different speeds in a material depending on their polarization direction. This results in the splitting of a single incident ray of light into two separate rays with different velocities. Materials that exhibit birefringence are said to be birefringent. Birefringence is commonly studied in the field of optics and materials science, where researchers investigate the effects of birefringence on light transmission, polarization, and other optical properties of materials. Additionally, birefringence is often used in technologies such as polarized light microscopy, optical filters, and liquid crystal displays. Researchers may also study birefringence in biological tissues or materials to better understand their structural and optical properties.