What Is Polarization of Light?

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Polarization of light occurs when electromagnetic waves exist in more than one dimension, and a polarizing light vibrates in one direction. Learn about the role of crystals in the polarization of light with help from a science teacher in this free video on physical science.

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Video Transcript

Hi, I'm Steve Jones and I'm going to explain what the polarization of light is. Now first of all, light as we know is an electromagnetic wave. And therefore we would expect something electromagnetic about the nature of light and we would expect waveforms. Well in the case of light, we expect there to be waveforms in three dimensions and here you can imagine a vertical waveform and a horizontal waveform around a direction of travel. So it's traveling in that direction but I've got a waveform like this and a waveform like that. That is a vertical waveform and a horizontal waveform. Actually with light, I'll have waveforms in all directions but it doesn't matter for what we want to do. Now many crystals and some materials polarize light. What this means is that this arrangement where we've got both vertical and horizontal components of the electromagnetic radiation waves, we won't have those components, we will only have a single component in a single direction. So if this were a wave like this and here's both the horizontal and vertical part going into this polarizing medium, what will come out is a wave which only has the vertical component, the horizontal component has disappeared because this is a vertical polarizer. Now when this gets to the next stage, where this is a horizontal polarizer, this won't get through because it will be absorbed and therefore nothing will get through. This is called crossed polars. So under crosses polars, we get nothing coming through. The first makes it vertical, the second removes the vertical component because that allows only horizontal components. In some cases, crystals can rotate the plane of polarization. That is it goes through the first part or goes into the crystal and it begins to rotate. So if I have two polars like this, two slices of polarizing material, one set vertically, one set horizontally and I put my crystal in here, this will rotate the plain of polarization so this polarization plane instead of being vertical when it hits, it will gradually rotate until it comes to here and some of it will get through. And this enables us to identify crystals. But the question was, what is polarization of light? And now I hope you understand what polarization is that we have electromagnetic waves in more than one dimension and a polarizing agent simply polarizes so it vibrates in one direction only. So that is what we mean by the polarization of light.

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