What is the difference in perception of polarized light and unpolarized light? What difference does polarized light cause to our eyes?
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$\begingroup$ None as far as I know. This is really a biology question - I'd like to know the answer though! I know that many cephalopods and some fish are sensitive to polarization - I wasn't aware of anything like this in humans but maybe there's still some very faint expression of a gene we picked up 300 million years ago ... $\endgroup$– Selene RoutleyCommented Dec 3, 2013 at 13:51
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2 Answers
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There is some evidence of polarization perception.
Many people are able to perceive polarization of light. It may be seen as a yellowish horizontal bar or bow-tie shape (with "fuzzy" ends, hence the name "brush") visible in the center of the visual field against the blue sky viewed while facing away from the sun, or on any bright background. It typically occupies roughly 3–5 degrees of vision, about the same size as the tip of one's thumb held at arm's length. The direction of light polarization is perpendicular to the yellow bar (i.e., vertical if the bar is horizontal). Fainter bluish or purplish areas may be visible between the yellow brushes (see illustration). Haidinger's brush may also be seen by looking at a white area on many LCD flat panel computer screens (due to the polarization effect of the display), in which case it is often diagonal.
See, for instance, Haidinger's brush on Wikipedia.
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$\begingroup$ In practice, Haidinger's brush is relatively hard to see on the blue background of the sky. It's much more prominent on the LCD screens with white background (and actually is also visible on AMOLEDs). $\endgroup$– RuslanCommented Mar 21, 2020 at 7:29
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$\begingroup$ @Ruslan Yep, I can easily see it on my phone, but never on the sky. $\endgroup$– jinaweeCommented Mar 26, 2020 at 13:29
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Our eyes cannot see any difference between ordinary (i.e., unpolarized) and polarized light. You can check it yourself, if you look through a polarizer (for example, some sunglasses have one). All you can notice is that the world gets slightly darker (because you block roughly half the incoming light). In addition, some reflections might be reduced dramatically (that is, after all, one of the main points in using polarizers in sunglasses).
There are, however, other species (e.g., bees, as far as I know) that can see the difference but, unfortunately, nobody has been able to ask them what such a difference looks like...
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$\begingroup$ So the only significant difference is due to decrease in intensity, and that too because the average value is halved. Thanks! $\endgroup$– ShubhamCommented Dec 3, 2013 at 16:50