No, I'm not just trying to look like Casey Neister here. This video is about this little P here, which means polarizing. So this video is about plain polarised light. Other channels cover the content, but gorillas it's going to help you get the A star. In this video, I'm going to show you everything you need to note a master the topic of polarisation. What the hell are you talking about now? So this type of sunglasses, polarising sunglasses, they have a vertical polarising filter in them. That means it cuts out any horizontally polarised light. And that's especially useful when you're skiing or doing water sports. Or when you're driving and you get a lot of glare off maybe the colours in front or puddles in the road. Essentially, these cut out horizontally polarised light, which is glare from all those things I just set. Polarisation has lots of uses though. So for example, this lens, this is a polarising filter that goes on top of a camera lens, just like the one I've got on my camera here. And what that means is that I can control the amount of light that's transmitted through this polarising filter just by rotating one of the two filters. So what there is there, so what there is here is actually two filters. And as I rotate one of them through 90 degrees, it actually cuts out all of the light. I know that's quite a difficult idea to get your head around. And that's probably because you're used to thinking of waves only having one kind of plane of oscillation. In fact, light electromagnetic radiation oscillates in all of the planes around the direction of travel of the wave. That's quite a hard idea to get your head around on a whatever. Be used to seeing waves on slingies modeled like this with the wave just oscillating in one plane around the direction of travel, in this case vertically. Unpolarised light is simultaneously oscillating in all directions around the direction of energy transfer. So I've got a little model here to help you imagine what's going on. I've got four planes over here, but you have to imagine the light oscillating in all planes around that axis. Plane polarised light is light, which is oscillating in only one plane. So that's unpolarised light that is oscillating in all directions. Our polarising filter is something just like this, which has bars in it, which cuts out oscillations in all directions apart from the one that it allows through. So that's what we mean by plane polarised means it's only oscillating in one plane. So this model polarising filter allows vertically polarised light through, but it doesn't allow horizontally polarised light through. You see it cuts out the oscillations when it's horizontally polarised light. And that's exactly what's going on in the polarising filters in the sunglasses. Transverse waves can be polarised. These blue cone things they are emitters and receivers are three centimetre microwaves. The grid acts as a polarising filter. When it's horizontal, it allows all of the microwaves to be transmitted. And it's vertical, the reading on the detector drops to zero. And when it's horizontal, back to maximum. And when there's nothing there, you see it's at maximum. So the filter will allow whatever direction whatever plane is or intake it with to wave it through, but it will stop all the oscillations in any other plane. You see it? It's pretty interesting. So if the filter is horizontal, it will allow horizontal to be polarised light to go through, but it will cut out that's what you think it might do. In just the same way, if we have unpolarised light like we do down here in the bottom left at this diagram, we have one polarising filter to turn that into polarised light. We'll cut out any other plane of oscillation apart from the one that is allowed through. And if we use a second filter and we can rotate that, then we can control the amount of light that gets through the system of filters. And that's really useful if you want to control the amount of light that's falling on a detector. We have unpolarised light being polarised by one filter. And then that plane polarised light is being then absorbed by another polarising filter. So the polarising filter is currently on the camera now and currently I've got them both orientated in the same direction. The front one is polarising the light into this horizontal direction, for example, and the second one is just allowing that through. And if I rotate the front one through 90 degrees, you can hopefully see that all the light is cut out. If I rotate back through another 90 degrees, more and more and more light is transmitted. And same again. So that's polarising filters. You can try this out with this awesome O-physics simulation. I'll put a link to this in the description. You've got your unpolarised light first of all, your first filter, making it vertically playing polarised light and a second filter that you can rotate. And you can see that as you rotate, the actual magnitude of that wave decreases with a cosine of this angle. Awesome simulations, go check them out. So we're going to question with this. They're always looking for the idea that if you take two polarised and you rotate one of them through 90 degrees, then you get this reduction of light. Get that word 90 degrees in, get that idea of the orientation of the two, like transmission being a maximum when they're orientated in the same direction and a minimum when one is at 90 degrees to the other. So now it's time to play, is it or is it not playing polarised? So if I take my polarising sunglasses and I show you the world through those and I rotate those from 90 degrees, is the light source behind me playing polarised? No, it did not really reduce in brightness at all. So those LEDs that are in that light back here, they are not playing polarised. And the interesting thing about this one, is that all the different colours have different polarisations. That's incidentally how 3D cinema works, is they have one polariser for one eye, one polariser for the other, and they display two images which overlap, one which is polarised in one direction, the other which is polarised in the other, so the left eye gets one image, the right eye gets another image, and your brain combines them into a 3D image. What about the computer screen? I hope that helps that's polarisation, it really helps to kind of see it. The only thing I guess I haven't talked about, is polarisation of horizontal surfaces, so imagine a wave of all those different orientations, hitting a flat surface, and it's only the horizontal orientation, which is going to reflect off, or the other orientations are going to be absorbed as they hit that flat surface. So that is why you get this partial polarisation of flat surfaces, and that's why these things are so good for skiing, or for driving, or for water sports, or for looking cool. It's because it's cutting out the glare on those horizontal surfaces like wet roads, like flat ski slopes, or like water. This is written in a slinky. Don't forget to subscribe and ring the bell, and check out grillifusies.com for all my videos organised by Topic. If you got that explanation, work for you just say yes sir in the comments. Thanks for watching!