Seeing the polarization of light with the naked eye

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DJ Mathson

Seeing the polarization of light with the naked eye

Post by DJ Mathson »

Haidinger´s brush - Seeing the polarization of light with the naked eye

Fascinating. I had never heard of this phenomena before, but apparently it has been known since the 1840s when Haidinger discovered the effect. You can determine the polarization of light by seeing a cross of yellow and blue "brushes" in the middle of your vision. I just tried this out by looking at a white surface, like a sheet of paper or my computer monitor, through a large polarization filter. It was very easy to see. It is easier to discover the blue and yellow brushes when you rotate the filter. The shape is approximately 2-3 cm (an inch) at an arm's length distance.

Next time there is a blue sky I will try to see the polarization of the sky light (wont need a polarization filter then). By using the Haidinger´s brush effect I was able to find out the polarization axis of my polarization filter (and from this determine that the polarization of a laser diode is parallel to the short axis.)

http://www.polarization.com/haidinger/haidinger.html

http://en.wikipedia.org/wiki/Haidinger%27s_brush
Tom B.

Seeing the polarization of light with the naked eye

Post by Tom B. »

Cool! I started to try it with a polarizer with my LCD monitor and was immediately reminded that LCD monitor screens are polarized at 45 degrees, probably to avoid weird polarization effects like this, so the observation would not work. A CRT would be fine. I was about to do the sensible thing - look at white paper under a desk lamp through my polarizer - when I remembered that I had some half-wave retarder film which rotates polarization 90 degrees, tried it on the monitor, and it worked! The effect is very subtle at first, but once you know what to look for it's not too difficult to see. I next tried paper under the desklamp with a regular polarizer. Once again, hard to see at first, but definitely there! Brightness is important - too bright and it gets washed out. Maybe gray paper would be better?

Thanks!
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