What Is Polarized Light?

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Polarized light is confined to one direction, and reflected light is polarized to some degree. Discover how polarized sunglasses work with help from a science teacher in this free video on physical science.

Part of the Video Series: Physical & Life Science
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Video Transcript

Hi, I'm Steve Jones and I'm going to explain what polarized light is. First of all, light as we know is an electromagnetic radiation. So any electromagnetic radiation consists of a wave of some kind. And this electromagnetic wave actually has three directions, there's the direction of travel, there is a what called a longitudinal wave and there are two transverse waves X and Y. That is these, there is a vibration in the magnetic field so light is basically a magnetic field, a changing magnetic field. Now if we look at it here, this is the direction it's traveling into the board and normal light is actually containing electromagnetic vibrations in all directions due to the fact that it's full of different atoms or aligned in different ways and doing different things. So it's kind of spread out in the way it transmits. Polarized light however is confined in direction to one or other directions. Any one of these directions you can polarize the light. So that the vibration is actually only in one direction. Now we don't normally recognize when light is polarized or not but in fact when you use polarizing sunglasses and you look at reflections from various objects, you can see that reflections actually are dimmer than they are if you don't use the sunglasses. And that is because the light actually is polarized. Polarizing sunglasses cut out reflected light so when you reflect light, it polarizes it to some degree. The other thing is in crystals you know these crystals that we see and they have particular structures, a lot of crystals because of the arrangement of the atoms in them, when light travels through them, the crystals cause the light to the polarized. Some crystals are very special and they cause the light that is already polarized to actually rotate the polarization, it changes the wave. So crystals have a very interesting relation to polarized light and some crystals are reactive to polarized light and some are not. For example a solid crystal, doesn't matter which direction you send light through it, polarized light through it, it has no effect on it whatsoever and so forth. So different types of crystal have different effects. But what this means is is light is polarized in this direction, then an object, a crystal which polarizes in this direction will stop that light passing through it because it will only allow light polarized in this direction to pass through it and therefore none will pass through and this is called crosses polars. So if you've got two polarizing materials then if you put them at right angles then no light will come through, if you line them up then the light will go through. So if you put them under crossed polars, no light gets through, but if you then insert a crystal which turns the polarizing sometimes light will get through. And this is a way we can look at different crystals. So basically polarized light is just about the direction of the magnetism and the electrical waves that are causing the light and polarized light has light, is light worthy waves are all in the same direction and it can be cut out by using a polarizer which is poles, which is polarized in a direction at right angles. So that basically is what polarized light is.

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