why do some windows (especially car windows) have a strange dark and light alternating pattern when wearing polarized sunglasses?

Question

why do some windows (especially car windows) have a strange dark and light alternating pattern when wearing polarized sunglasses?

In: 21

Answer 1

Because they themselves are laminated and that causes light reflected from them to be polarized, which in turn creates the interference pattern you see through another layer of polarizing film in the sunglasses.

For a fun trick try looking at your cell phone, or even a calculator or other digital display and rotate the device to see similar effects of cross-polarization.