The vivid colors and patterns you see are a result of birefringence. Birefringence is an optical technique that can be used to determine the structural orientation in a transparent material by looking at the changes in the polarized light that is passing through. Usually light waves travel in all directions, but polarized light waves are travelling in only one direction (horizontal or vertical).
When you put a transparent material, like the plastic dish and tube in the image, in between two polarizers that are oriented perpendicularly, only the light that has been rotated by the material will pass through. Stress in the material changes the microscopic structure which rotates the light waves shining through, and we see this as bright patterns and colors aka birefringence.
Department of Physics and Astronomy
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