If you rotate a pair of polarizing sunglasses, you will find that they cut road glare much better in some positions than in others.

When light reflects from water, asphalt, or other non-metallic surfaces, it becomes polarized. That is, the reflected light is usually vibrating more in one direction than in [...]

When certain plastics are placed between two pieces of polarizing material, their stress patterns become dramatically visible in a brightly colored display. A stressed plastic object can be used to illustrate stresses found in bones.

Overhead projector and screen
2 polarizing filters (If polarizing material is not readily available, you can use two lenses from [...]