Thursday, 2 April 2015

Did you know...that humans can see polarised light?

Light can be defined as a waveform. In normal light, the waves swing in all possible directions. When light is filtered so that all the light waves have the same direction, it is called polarised light. This is how polaroid sunglasses work, for example. Scientists use polarised light for studying mineral structure, and some say that animals may use patterns of polarised light in the sky for navigation.

This is what it looks like to me
Computer screens emit polarised light. This is a side effect of the way they work. The outer layer of a LCD screen is a polarising filter. It is possible to see this with our own eyes. This effect is called Haidinger's Brush.

It is easiest to see this if you stare at the screen for a few moments, then quickly tilt your head to the side. To me, the effect usually looks like a yellow, butterfly-shaped pattern, about 2 cm/1 inch wide. Once you have seen it, you can't unsee it!

Some people can see this effect also in the sky, especially close to the horizon where the daylight is most polarised.

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