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Polarization of light waves

Random polarizationIt turns out that any light wave can have lots of possible orientations. It may be vibrating in the up-and-down, or maybe the side-to-side.  This is what we call random polarization because the waves are randomly oriented or polarized.  (It has nothing to do with the color of the light.)

 

PolarizationThe polarizer (invented by Polaroid) removes all of the possible orientations except one.   We could visualize a polarizer as a "picket fence" .  The picket fence is actually a series of metal lines within plastic or glass.

Two polarizers at right angles to each other, will block out all orientations of light.  No light would get through.

No light gets through

The video below shows a polarizer held in front of a camera which has another polarizer in front of it.  As the polarizer is turned, it goes from light to dark.    It appears light when the "pickets" of one polarizer match the "pickets" of the other  polarizer.  The polarizer appears dark when the two sets of "pickets" cross at right angles and allow no light through.


[same clip without lines drawn in.]

Glare is light that bounces off a horizontal flat surface, like water or the road. This makes it difficult to see what is below the water because the glare is too bright or difficult to see the road surface. As a result of the flat surface it ends up being polarized in the same plane as the surface.  Driving or Fishing glasses can eliminate this glare by having polarizers that do not allow horizontally polarized light to come through.  This restricts the glare and makes it easier to see road or what is under the water.

glare is horizontally polarized

The image below shows you the effects of removing glare by using a vertically aligned polarizer.  Notice how the polarized side has much less glare.  You can actually see more of the inside of the car.  Also the bright spot on the hood is gone. [Click here to see several more glaring comparisons]

Glare removed by polarizer.