Start typing, then use the up and down arrows to select an option from the list.

Physics32. Electromagnetic WavesPolarization Filters

Okay, one thing that we need to talk about is this idea of polarization. Okay, and this is going to come back again later on when we start talking a little bit more about optics, but when we say polarization what do we mean? Polarization is the direction of the E field. Okay, this is just how it's defined. So for instance if my wave has an E field that's going up and down, then we say that it has vertical polarization. Okay, we don't really care about what the B field is doing, it's just defined in terms of the E field. But if you have a wave where the E field is in and out of the board like so, then this is called horizontal polarization. Okay, so this -- these are the two polarizations for an electromagnetic wave, either horizontal or vertical, and things like lasers have a preferred orientation for their electric field. Okay, they either come out vertical or horizontal. But things like sunlight have all different polarizations. Okay, they have a vertical component, they have a horizontal component, and then they have all the different angles in between. Okay, so incandescent sources like sunlight, like a light bulb, those will have random polarization, whereas lasers will have defined polarization. So you're familiar with this because of two things. One, is you might have sunglasses that are polarized. Okay, and what polarized sunglasses mean is they block one of these polarizations. It turns out that the glare off the ocean or the glare off a wet street is dominantly polarized in one direction and so if you put on your sunglasses to just block that particular polarization, you essentially cut out the glare. Okay, so when you look at the ocean you see a bunch of glare, put on your polarized sunglasses, the glare goes away, and that's because that glare is polarized in one direction, your polarized sunglasses block it. But this is also used in things like 3D movies. Okay, 3D movies take advantage of polarization, and basically they use a different polarizer for each eye. Okay, so if you go to a 3D movie and you get those glasses, what those glasses are doing is there's a different polarization on the left eye than on the right eye, and so when they project it on the screen with a certain polarization from the lamp, and they use some polarizers to do it, they're creating a different image for your left eye than your right eye. So now when you put them back together, it looks like a 3D picture to you.