Sunglasses: Newsletter Challenge (04/05/05)

But I'd side with the daughter. I know sunglasses use polarizers to block the sunlight so I assume he's basically rotating a polarizer. However, the sun emits equal quantities of each kind of polarization, unless the atmosphere is polarizing the light in some way, I'm afraid his sister's right, he is a moron.

Here is a list of reasons:
1) If he is holding the glasses so that the sun shines through them onto a flat surface like a sidewalk; you can see an image of the sun more clearly and safely.
2) By holding the glasses an arms length away and looking at an object with horizontal and vertical lines you can see the amount of lens distortion in your sunglasses. (This distortion can lead to headaches and eye fatigue if you wear them too long.)
3) If the lenses are polarized he can be using them to find places the sky has partially polarized light. That is because the light coming from some parts of the sky is partially polarized.
Can anyone think of any other reasons?

Actually, he's looking for the ISS (International Space Station) and the orientation of the glasses do effect one's ability to detect such a large object orbiting the earth during daylight hours.

Answer: He's testing to see if the glasses are polarized or not. If they are, the light coming through the lens he's looking through will brighten and darken as he rotates the glasses. (Light from a blue sky is polarized.) If he had another pair of sunglasses that he knew was polarized, he could rotate a lens of the one he's testing in front of a lens from the known polarized glasses, and if the test pair's lens was polarized he'd see the light coming through lighten and darken as he rotated them. Polarized glasses are very useful for eliminating glare because they tend to eliminate horizontally polarized light, and the light reflected off of a road or another car or even a water surface is strongly horizontally polarized. (This is why fishermen use them - the surface glare is drastically reduced and you can see into the water. Rotate them 90 degrees, however, and just about all you'll see is surface glare!) There are some nice discussions of this at http://www.polarization.com/water/water.html and http://www.howstuffworks.com/sunglass.htm/printabl e.

As reported in the 04/12 edition of Specs & Techs from GlobalSpec:

He's testing to see if the glasses are polarized or not. If they are, the light coming through the lens he's looking through will brighten and darken as he rotates the glasses. (Light from a blue sky is polarized.) If he had another pair of sunglasses that he knew was polarized, he could rotate a lens of the one he's testing in front of a lens from the known polarized glasses, and if the test pair's lens was polarized he'd see the light coming through lighten and darken as he rotated them. Polarized glasses are very useful for eliminating glare because they tend to eliminate horizontally polarized light, and the light reflected off of a road or another car or even a water surface is strongly horizontally polarized. (This is why fishermen use them - the surface glare is drastically reduced and you can see into the water. Rotate them 90 degrees, however, and just about all you'll see is surface glare!) There are some nice discussions of this at http://www.polarization.com/water/water.html and http://www.howstuffworks.com/sunglass.htm/printabl e.

Just checked this out - rotate the glasses against the blue sky and sure enough, dark to light to dark. Cool. Haven't yet checked out the Babe Winkerman effect of being able to see that prize fish (or any fish) through the surface of the water.