Editing Polarization (waves) (section)

=== Measurement of stress ===
[[File:Polarized Stress Glasses.jpg|thumb|Stress in plastic glasses]]
In [[engineering]], the phenomenon of [[birefringence#Stress-induced birefringence|stress induced birefringence]] allows for stresses in transparent materials to be readily observed. As noted above and seen in the accompanying photograph, the chromaticity of birefringence typically creates colored patterns when viewed in between two polarizers. As external forces are applied, internal stress induced in the material is thereby observed. Additionally, birefringence is frequently observed due to stresses "frozen in" at the time of manufacture. This is famously observed in [[cellophane]] tape whose birefringence is due to the stretching of the material during the manufacturing process.