stress-optical law

The stress-optical law states that when a transparent material like glass or plastic is stretched or compressed, it changes how it bends light passing through it. Specifically, the amount of light birefringence—where light splits into two rays traveling at different speeds—is proportional to the internal stress within the material. This relationship allows scientists to determine the stress distribution inside a material by examining how it affects polarized light passing through it, making it a valuable tool in materials testing and engineering to assess internal stress without damaging the object.