Polarized Sunglasses

Discussion in 'Love & Lifestyles' started by Nixy, Dec 6, 2008.

  1. Nixy Princess Consuela Banana Hammock Elimi-nistrator

    So, I was sure there was a thread about this very topic (or a thread that spoke to this very topic) where Prof and I had a bit of a back and forth about sunglasses and why he thought the last pair I bought (almost 3 years ago) should have been polarized. Well, I just bought new prescription sunglasses and they are polarized. So, I would like Prof (and anyone else who wants to) to tell me why I made a good decision. Everything I've ever heard or read suggests they're better...but WHY are the better. What did I pay an extra $66 for?
  2. Altron LIKE A BOSS!!!!! Well-Known Member

    they will make light reflected off of things less bright.

    polarization is the 'tilt' of light. think of light as a sine wave, but it can be tilted in any direction.

    polarization allows only the component of the light that's in a specific direction to be passed through. remember dot product from Freshmen Physics or from Vector Calculus? polarization works like that.

    For instance, if you have a polarizer with a horizontal transmission axis, it only lets the horizontal light through. if you have a horizontal wave, it all goes through. if you have a vertical wave, none of it goes through. if you have a wave of amplitude "A" and angle "theta", the amount of light passed through is Acos(theta). Since the light intensity is the square of the amplitude, you get I = Io * cos^2(theta), which is called Malus' Law, where I is the intensity of the light you see, Io is the initial intensity, and theta is the angle between the transmission axis and the polarization of the light.

    Now, since natural light is polarized in all random directions (we can say 0 < theta < 2pi), we can find the average I of randomly polarized light.
    I = Io/(2pi) multiplied by the integral from 0 to 2pi of cos^2(theta)
    The result of this is that I = Io/2
    That is to say, looking at randomly polarized light through a polarizer, half of the light passes through. this doesn't affect how you see objects, just the brightness.

    but that's just for objects lit by randomly polarized natural light.

    the fun part of a polarizer is when we get into coherent light. coherent light is all polarized exactly the same. usually it comes as a result of reflection off of a glossy surface, such as a car's paint, or water, or something like that.
    now, we go back to Malus law. If the transmission axis is perpendicular to the coherence axis, none of the light will go through!!!

    the effect of this is that if you have coherent light reflected off of a television, or a car, or a lake, polarized sunglasses will remove that light, while keeping the rest of the light.

    now, the one issue is that you may have trouble viewing certain things. For instance, i used to have polarized sunglasses, and if I had to use my cell phone, i needed to take them off, because the polarization blocked all the light coming from the phone's screen.
  3. Nixy Princess Consuela Banana Hammock Elimi-nistrator

    hmmmm interesting. I am excited to do some driving with these on! I plan to drive to Banff tomorrow to do some Christmas shopping, should be fun :)
  4. tonksy Hitting the egg nog New Member

    Is polarized the same as "glare proof"? My fav eyeglasses are glare proof. My secondary pair is not and that is the reason they are my secondary pair.
  5. BB BB New Member

    So, Altron, how did you finally get on with that bird at work????

    Man, you were obsessed with her as i recall :)

    Best BB
  6. Inkara1 To err is human. To arr is pirate. Well-Known Member

    That's ancient history. He's got an actual girlfriend now, that he met in college. No one knows if he's gotten it on with the girlfriend (they've been together for something like a year and a quarter now) and after asking over and over, we've pretty much given up.
  7. BB BB New Member

    Heh :)

    ...nothing much changes then - ROFL
  8. BB BB New Member

    So... Altron ...
  9. Altron LIKE A BOSS!!!!! Well-Known Member

    i am very very mysterious
  10. Gonz Founding Member and Vast molṑn labé

    If you care, there are about 300 pages worth of ShoutBox where we learned, in detail, about his coming of age.

    Search for the Edge of Young & Restless college boys.
  11. GrandCaravanSE Derby Guys Bang Harder! Active Member

    They help a little but don't waste your money stick with the cheap ones, you loose the expensive ones anyway:glasses:
  12. Nixy Princess Consuela Banana Hammock Elimi-nistrator

    Well, first of all I already bought the polarized lens. Secondly, there is no such thing as cheap prescription sunglasses.
  13. tonksy Hitting the egg nog New Member

    Yeah, not to mention that you are more likely to wear them when they have no glare.
  14. Inkara1 To err is human. To arr is pirate. Well-Known Member

    When you wake up in the morning and the light hurts your head
    The first thing that you do when you get up out of bed
    Is hit the streets a-runnin' and try to beat the masses
    And go and get yourself some cheap sunglasses

    Oh yeah
    Oh yeah

    I spied a little thing and I followed her all night
    In her funky fine Levi's and her sweater's kinda tight
    She had a west coast strut that was sweet as molasses
    But what really knocked me out was her cheap sunglasses

    Oh yeah
    Oh yeah

    Now go out and get yourself some big black frames
    With the glass so dark they won't even know your name
    And the choice is up to you, 'cause they come in two classes:
    Rhinestone shades or cheap sunglasses.
  15. Professur I'm just a fungii. Well-Known Member

    Ok, polariod sunglasses. Let me start by saying congrats on a good choice.


    Why. You know when the car in front of you lines up just perfectly with the sun behind you and you get flashed? Say goodbye to that. When your windshield isn't all that clean and you pass from shade to sun and the glass lights up like a neon and you can't see through it? No longer a problem. You like to ski? No more gritty eyes from snowglare.
  16. GrandCaravanSE Derby Guys Bang Harder! Active Member

    Oh, sorry i did not see the perscription part of that post. i though you were talking about just regular sunglasses, well i just buy the cheap ones cause i always loose them.
  17. Nixy Princess Consuela Banana Hammock Elimi-nistrator

    You also missed the part where I said I already bought them and the part where I said I bought my last pair of sunglasses almost 3 years ago (indicating I don't just randomly lose sunglasses).
  18. Nixy Princess Consuela Banana Hammock Elimi-nistrator

    Awesome :D

    I am going to learn to snowboard this winter!
  19. Professur I'm just a fungii. Well-Known Member

    Didn't you say that last year too?
  20. Nixy Princess Consuela Banana Hammock Elimi-nistrator

    Nope, last year I said ski. That didn't go so well...the boots and I don't get along so well.

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