Physics 2000 Einstein's Legacy Laptop Screens

Light Through Liquid Crystals

Before , you said that a liquid crystal could somehow rotate the polarization of light--how does that work? Do the french-fry molecules act like little polarizing filters?

Yes and no. The liquid crystal molecules do affect the polarization of light, but they do it in rather a different way than the filters we discussed earlier. A polarizing filter works by absorbing a particular component of the electric field...

Yeah, I remember--it's like a gate that only lets through light polarized in a certain plane.


Right. Well, the liquid crystal molecules don't absorb anything; they let all the light through. However, if they're arranged in the proper way, they can "twist" the light--that is, rotate the plane in which it is polarized.

So if polarized light goes through the molecules, it comes out polarized in a different direction--but would anything happen if the incoming light were unpolarized?

No--that's why the light is sent through that first polarizer before it enters the liquid crystal.

What did you mean by "arranged in the proper way"?



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