Task: Text Categorization
Input (English): It can occur in crystals lacking a center of symmetry via the Pockels effect. Nicol and Wollaston prisms utilize this property through the application of (*) calcite. When an electric field is applied to an anisotropic transparent substance, it occurs through the Kerr effect and it arises in materials possessing two different indices of refraction. For 10 points, identify this optical phenomenon that divides unpolarized light into an ordinary and an extraordinary ray traveling in different directions.
Output (English): Science