Polarization

The direction of the electric field component of an E-M wave defines its plane of polarization
Most sources of light produce waves with electric fields at all orientations perpendicular to the direction of travel: this mix of waves is unpolarized
A few sources of light produce waves with their electric fields preferentially oriented in one particular direction: we call this polarized light
Unpolarized light can be polarized by passing it through a special filter which absorbs waves which have their electric fields perpendicular to its axis of transmission
Two polarization filters can block all light from passing through them if they are oriented with axes perpendicular to each other
Light can also be polarized if it scatters or reflects off molecules or a surface
Malus' Law describes the intensity of polarized light which passes through a second polarizing filter, oriented at some angle to the light's plane of polarization
Liquid crystal displays (LCDs) are one very common and important application of polarization.

Here's one example of the difference a polarizing filter can make:

Image courtesy of blueshark

Take a look at a pair of images, one taken through a polarizing filter, the other without any filter.

Images courtesy of the Robotic Antarctic Meteorite Search project

Example: You and your friend Joe are wearing polarizing sunglasses. As you look out on a sunny day, the sunlight is so bright, it nearly blinds you. "Argh," you cry, "if only I could cut this light down to 10% of its current level -- THEN my eyes would be comfortable." "No problem," says Joe. "Here -- take my sunglasses and hold them in front of yours. If we just rotate my pair by the right angle, the light reaching your eyes will drop to 10% of its current level."



       Q:  By what angle should Joe rotate
           his sunglasses as he holds them
           in front of your eyes?


           (and is this really going to work
            very well in practice?)

For more information

Detailed information on color TV LCD displays

Information on color LCD displays from entertainmentcenterspot.com