double refraction

Double refraction, also called birefringence, occurs when light passes through certain types of transparent materials, like quartz or calcite. These materials have a unique internal structure that splits incoming light into two separate rays, each traveling at different speeds and directions. As a result, when you look through such a material, you see two overlapping images or a distorted view. This effect happens because the material's internal layers influence how light waves move, causing them to diverge. Double refraction is useful in optical devices and helps us understand the internal properties of certain minerals.