Using light polarisation to hide your face #science

[qcontinuum]

In short, it's the reason polarized sunglasses make your cellphone screen difficult to see when the phone is turned 90°.

[brendondavid]

I love when someone is doing a visual demonstration of something and the cameraman does everything in his power to not capture it

[tristan]

A third one will really mess up your understanding of reality

[TheJamation]

Why’d I think this guy was a lawyer presenting to a jury at first

[FoldingScreenMonkey]

Fun fact: when the two are perpendicular, adding a 45deg one in the middle will let you see again

[ujiltromm]

And the reason for it is that polarization changes how the light waves travel. Light polarization is chaotic, a polarizer makes it non-chaotic, all photons that pass through it are at the same angle. Then you try to pass them through a polarizer that is 90° off, and they have 0% chance to make it through.

Now if you try to pass them through the next polarizer, they have a chance of 1-((angle° mod 90)/90) to make it through, and this chance corresponds to the luminosity multiplier: at 45°, you'll get 0.5× the luminosity.

And this is why the third polarizer at 45° in-between the two at 90° allows 25% of the luminosity through.

[vwlz]

Thats not even the interesting part.... usually this demonstration involves adding a third polarizer and making it brighter, which doesnt make intuitive sense

[lukem]

Thanks for explaining how to hide my face using polarising filters. I'm going to use this tomorrow at work.

[ZS-bgjo]

*circular polarization has entered chat*

[cooljunkproductions]

"The hallmark of polarization is you go from maximum intensity, to minimum intensity, to maximum intensity" - US Congress: *Takes notes*

[matthewspence]

2 polarizers are fun, but 3 is mind blowing

[anonanon]

I'm amazed that this video hasn't been censored by the YouTube thought police for being too polarising.

[karthickc]

This is how every LCD screen works. Have two polarizing filters (kept 90 degree to each other so they block all light going through) with a liquid crystal sandwiched between them. When the individual pixels of liquid crystals are powered by an electric potential they literally rotate light and enable light to pass through the second polarizer! That is how you turn pixels on and off. If the pixel is off light gets blocked since both the polarizers are perpendicular to each other. If the pixel is on the liquid crystals will rotate light to enable light to pass through the second polarizer.

[dobbsconnor]

This how I test sunglasses with my phone

[BeyondTheMind]

They should make side tints for your windows like this, so you can block out those awkward people when you're sitting at the lights

[janernn]

That's how variable neutral density (ND) filters work in photography

[matthewkendall]

I recall a physics demo when you add a third sheet really trippy things happen - they get lighter when you absolutely expect it to get darker and this was I recall due to qunatum effects - what an amazing world we live it!

[RetroRob]

"And adding a third one would reduce our earth to rubble.."

[ORam...]

So this is what Mark Cuban has been up to.

[dreammfyre]

Why is this guy in a suit showing us polarizers 💀