Tuesday, November 25, 2014

Polarization of light

Polarization is one of those things I assumed I understood but I really didn't. Sam is always going on and on about it (every time he wears his sunglasses he notices some new effect to make observations about) but now I finally, at least somewhat, understand what is making these effects occur! 

We watched this Happy Scientist video, and then this one, which gave great explanations of what is happening when light is polarized. He describes the phenomenon of birefringence (which is what we're seeing in that CD case pictured above—the photograph was taken through our polarizing filter) and shows how you can use two polarizing films together to twist the light back so you can see through it again! Like this:
Polarized sunglasses: at this angle they are darkening the computer's LCD screen slightly, but not blocking all the light, because they aren't turned in the same direction the (already-polarized) light from the screen is coming from.
When we turn the glasses, they now block all the polarized light from the screen.
But, if I hold another polarizing film up behind the glasses and twist it at an angle halfway between the others, it actually undarkens (??) the screen, and makes a window we can see through! So cool!

A few more good links: 

A video about polarization filters

This experiment shows how you can change the direction of polarization in light

A website entirely about polarization

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