How does polarised sunglasses work
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Light travels through the air kind of like a dolphin jumping behind a boat, in a straight line, but also Up/Down motion. Since light goes up/down so quickly you can think of it less as a laser point, but more of something like a 2×4 flying vertically through the, it has a definite “height” to it’s motion.
BUT most light sources aren’t “in sync” with each other, meaning some light is going up down, some side to side, some every possible angle in between.
So a polarized filter is basically just like a set of window blinds, tons and tons of tiny slits stacked on top of each other. Imagine a 2×4 coming through window blinds, *only* 2x4s that are perfectly sideways can squeeze between the slits perfectly. Any other orientation of 2×4 would hit the slats and get caught. That’s a polarizing filter.
Since “scattering”, like reflections off a wet road, cause this crazy variance in light, filters like this help reduce “Glare” caused by the scattering by forcing only one orientation of light through the slats.
Most TVs and cellphone screens have a filter on them now at the source, you normally don’t notice it but if you wear polarized sunglasses and tilt your head while looking at your phone or TV, you’ll notice the image appears and disappears. That’s what’s happening, the screen is only emitting light in a very specific orientation, and your glasses are blocking that orientation so the screen appears “dark” to you.
Imagine light as a wave. It wiggles up and down like a wave on a string does. However, the direction it is wiggling can vary between different light waves. One wave might wiggle up and down while another might wiggle left to right, and a different light wave might wiggle anywhere in between.
Polarizers have material in them that is really good at absorbing light waves ONLY if they are wiggling in a specific direction. For example, a polarizer might only be good at absorbing waves that are wiggling up and down, but it wouldn’t absorb light that is wiggling left to right.
Most light that we interact with is unpolarized, that means that the direction that all billions of individual waves of light are wiggling in random directions. If you pick 1 at random you might get one wiggling up and down, you might get one wiggling left to right, or you might get one wiggling somewhere in between up and down and left to right. This means polarized sunglasses will block all the light that is wiggling up and down but leave all the light that is wiggling left to right, which will reduce the amount of light that gets to your eyes making things seem darker.
What is really cool about polarized sunglasses though is that when light reflects off of a surface, like the surface of water, it actually forces the reflected light to wiggle in a very specific direction, this means the light becomes polarized. If you are wearing polarized sunglasses that are specially designed to block this reflected light then it becomes much easier to see into the surface of the water, because all of the reflected light that would normally block your vision into the water because it’s too bright would get blocked, while all the light that originated from underneath the water would get through and be unpolarized so you can see it.
Light travels through the air kind of like a dolphin jumping behind a boat, in a straight line, but also Up/Down motion. Since light goes up/down so quickly you can think of it less as a laser point, but more of something like a 2×4 flying vertically through the, it has a definite “height” to it’s motion.
BUT most light sources aren’t “in sync” with each other, meaning some light is going up down, some side to side, some every possible angle in between.
So a polarized filter is basically just like a set of window blinds, tons and tons of tiny slits stacked on top of each other. Imagine a 2×4 coming through window blinds, *only* 2x4s that are perfectly sideways can squeeze between the slits perfectly. Any other orientation of 2×4 would hit the slats and get caught. That’s a polarizing filter.
Since “scattering”, like reflections off a wet road, cause this crazy variance in light, filters like this help reduce “Glare” caused by the scattering by forcing only one orientation of light through the slats.
Most TVs and cellphone screens have a filter on them now at the source, you normally don’t notice it but if you wear polarized sunglasses and tilt your head while looking at your phone or TV, you’ll notice the image appears and disappears. That’s what’s happening, the screen is only emitting light in a very specific orientation, and your glasses are blocking that orientation so the screen appears “dark” to you.
Imagine light as a wave. It wiggles up and down like a wave on a string does. However, the direction it is wiggling can vary between different light waves. One wave might wiggle up and down while another might wiggle left to right, and a different light wave might wiggle anywhere in between.
Polarizers have material in them that is really good at absorbing light waves ONLY if they are wiggling in a specific direction. For example, a polarizer might only be good at absorbing waves that are wiggling up and down, but it wouldn’t absorb light that is wiggling left to right.
Most light that we interact with is unpolarized, that means that the direction that all billions of individual waves of light are wiggling in random directions. If you pick 1 at random you might get one wiggling up and down, you might get one wiggling left to right, or you might get one wiggling somewhere in between up and down and left to right. This means polarized sunglasses will block all the light that is wiggling up and down but leave all the light that is wiggling left to right, which will reduce the amount of light that gets to your eyes making things seem darker.
What is really cool about polarized sunglasses though is that when light reflects off of a surface, like the surface of water, it actually forces the reflected light to wiggle in a very specific direction, this means the light becomes polarized. If you are wearing polarized sunglasses that are specially designed to block this reflected light then it becomes much easier to see into the surface of the water, because all of the reflected light that would normally block your vision into the water because it’s too bright would get blocked, while all the light that originated from underneath the water would get through and be unpolarized so you can see it.
Light reflected at glancing angles off off non-metal surfaces is strongly polarized parallel to the plane of the surface (this is basic physics quantified by Snell’s law and Fresnel coefficients).
The the light that typically causes ‘glare’ in strong sunlight is therefore horizontally polarised.
The general light of a scene is otherwise mostly unpolarized.
Polarising sunglasses pass vertically polarised light, but block the horizontal polarisation of the glare. In this way they make most of the scene 50% darker, but make the glare much much more than 50% darker, making for more comfortable viewing.
By way of experiment, if you were to put your head on its side (or rotate the glasses through 90 degrees) the glare would be passed at near full-strength, while the rest of the scene is attenuated by 50% – making the glare worse!
Similarly, if you look at glancing-angle reflections in windows through polarising glasses, you will see the reflections come and go as you rotate the glasses.
Light reflected at glancing angles off off non-metal surfaces is strongly polarized parallel to the plane of the surface (this is basic physics quantified by Snell’s law and Fresnel coefficients).
The the light that typically causes ‘glare’ in strong sunlight is therefore horizontally polarised.
The general light of a scene is otherwise mostly unpolarized.
Polarising sunglasses pass vertically polarised light, but block the horizontal polarisation of the glare. In this way they make most of the scene 50% darker, but make the glare much much more than 50% darker, making for more comfortable viewing.
By way of experiment, if you were to put your head on its side (or rotate the glasses through 90 degrees) the glare would be passed at near full-strength, while the rest of the scene is attenuated by 50% – making the glare worse!
Similarly, if you look at glancing-angle reflections in windows through polarising glasses, you will see the reflections come and go as you rotate the glasses.
? Polarised sunglasses work by blocking out light that is reflected off of surfaces like water, snow, and glass. The lenses are coated with a special chemical that absorbs the reflected light, reducing glare and making it easier to see in bright conditions.
? Polarised sunglasses work by blocking out light that is reflected off of surfaces like water, snow, and glass. The lenses are coated with a special chemical that absorbs the reflected light, reducing glare and making it easier to see in bright conditions.
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