How Everything Works
How Everything Works How Everything Works
 

QUESTIONS AND ANSWERS
 
Question 1192

Could you explain the meaning of polarization in optics? Please try to associate it with water waves if possible, to help me visualize it, and avoid the use of electric and magnetic fields. — AM, Yavne, Israel
I can't completely avoid electric and magnetic fields because polarization in optics is associated with a wave's electric field. I also can't depend entirely on water waves because they only have one (transverse) polarization. Still, I will try.

First, consider a wave traveling toward us on the surface of a lake. Suppose that this wave passes under a small boat and I ask you which way the wave is making the boat move. You would tell me that the boat is moving up and down. I would then tell you that the wave is vertically polarized because it causes objects that it encounters to move up and down rhythmically.

Unfortunately, pure water won't do for the next step because it won't support horizontally polarized waves. So let's imagine that some ecological disaster has turned the entire lake into gelatin. An explosion at the side of the lake now causes a wave to begin heading toward us on the gelatin lake, but this strange wave involves a side-to-side motion of the lake's surface. Now when the wave passes under the boat, the boat moves side-to-side rhythmically. In this case the wave is horizontally polarized because it causes objects that it encounters to move left and right rhythmically.

Now let's return to optics. When an electromagnetic wave heads toward us, its electric fields will push any electrically charged particles it encounters back and forth rhythmically. If we watch one of these charged particles as the wave passes it and observe that this particle moves up and down, then the wave is vertically polarized. If instead the charged particle moves left and right, then the wave is horizontally polarized.

         

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