Fun With Polarization

I lost my sunglasses clips a while ago, so while I was back in Boston, I picked up a new set. Interestingly, they are polarized sunglasses—it's the first time I've ever worn them.

The first noticeable effect was driving down the road, and seeing moiré-type patterns in the rear windshields of some cars. Also, I remember hearing that polarized glasses reduce glare, and I wondered how they do that—i.e., does it know bad light vs. good light? This prompted a look at the Wikipedia article.

It explained that the glare-reduction is due to polarization cutting the light from horizontal reflecting surfaces—I assume that polarized sunglasses are oriented to maximize the effect. I didn't realize that reflections themselves caused (at least some degree) of polarization.

Then I got to the sentence about LCD screens: The role played by polarization in the operation of liquid crystal displays (LCDs) is also frequently apparent to the wearer of polarizing sunglasses, which may reduce the contrast or even make the display unreadable. I said, "Cool!," instantly grabbed my sunglasses, turned off the lights, and started staring at my laptop's monitor. When I turned my head about 45 degrees to the left, the image went black. Neat!

Yeah, it was definitely a geeky way to spend the evening. But dad is in full-on Jabba the SportsFan mode (parked in front of the TV watching World Cup Soccer for most of his waking hours), so DVD movies were not an option.