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by asrahfatin on March 24th, 2007

asrahfatin

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How can you tell if a pair of sunglasses is polarizing or not?

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  • by Anonymous on March 24th, 2007

    Anonymous

      If you have two pairs of sunglasses, then an easy test is to arrange them so that you are looking through both at the same time.  Rotate one of them 90° relative to the other.  If both pairs are polarized, then the view through both will become much darker as you rotate one away from the other.  If you see this effect, then you can know that both pairs are polarized.  If you do not see this effect, then you can know that at least one pair is not polarized.

      Sunglasses are polarized to admit mostly light that is polarized vertically, and to block light that is polarized horizontally.  If one pair is turned on its side, then it will admit horizontally-polarized light, while blocking vertically-polarized light.

      Have a look at the two pictures below.  I'm afraid they don't show it as well as I could hope, but at least you can see how to conduct the test.  In the second picture, where the two pairs of sunglasses are turned 90° from each other, the view through the point where the two lenses overlap is very dark.  Where they are turned the same way, the view through the overlapping lenses is not that much darker than the view through just one lens.

      The reason that sunglasses are polarized vertically is that most unwanted glare consists predominantly of light reflected off of horizontal surfaces; and therefore tends to consist of light that is mostly polarized horizontally.  By admitting mostly vertically-polarized light, and blocking mostly horizontally-polarized light, sunglasses thus block more of the unwanted glare, while blocking less of the useful light.

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  • by Glenn Blaylock on March 24th, 2007

    Glenn Blaylock

    Let me just add a little to my brother's answer. He noted that most of the glare coming off of surfaces is horizontally polarized. So, polarized sunglasses are polarized to cut out this glare. Therefore, a test that you can conduct with one set of sunglasses, is to go outside and look for some glare coming off of a horizontal surface. (This is easiest to do shortly after sunrise or shortly before sunset looking at where the light is reflecting off of a road surface.) While holding the sunglasses in front of your face, look through one lens and rotate the glasses. Does the amount of glare that you see change as you rotate? If so, then you have polarized lenses. If not, then you don't.

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  • by JUSTNORMAL on March 24th, 2007

    JUSTNORMAL

    I always wear Polarized Sun glasses, and buy them at Sunglass Hutt at the Mall. It states on them, whether they are polarized or not, or you must ask the clerk. They also sell them in nearly every eye glass facility. If you have a pair and not sure, just look into the sun. If you have to squint, then they are not polarized

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  • by Anonymous on August 19th, 2008

    Anonymous

    Just put the glasses on and look at a computer (LCD) screen. Slowly tilt you head each direction, if they are polarized, you will see the screen get darker and lighter as you tilt your head and there may be a point where you will not be able to see the screen at all

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  • by asrahfatin on March 24th, 2007

    asrahfatin

    If you are purchasing new sun glasses and want polarized lenses, take 2 pair and hold one with the ear pieces in the normal way they would be worn and put the others in front or behind cross ways and look through both sets of lenses.. there should be no light coming through them. You can test this by moving one set or the other to the same angle to where they match and the light will come through. (This only works with polarized lenses on BOTH pair of sun glasses).

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