This tests your understanding of light | Optics puzzles 1

The barber pole effect of shining polarized light into sugar water.
Next video: • How wiggling charges g...
Steve Mould's video on the topic: • Why Sugar Always Twist...
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An equally valuable form of support is to simply share the videos.
Thanks to Quinn Brodsky for setting up the demo and to the MIT Physics Instructional Resources Lab for their help and materials, especially Josh Wolfe and Caleb Bonyun.
Thanks to these viewers for their contributions to translations
German: Josh, jns-v
Hebrew: Omer Tuchfeld
Hungarian: MrExpert
Indonesian: akhyarr
Italian: Gabboronco
Korean: @tebaioioo, Juhyung
Persian: ah.202
Russian: fedor, ilevinson
Spanish: Marcelo Lynch
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These animations are largely made using a custom Python library, manim. See the FAQ comments here:
3b1b.co/faq#manim
github.com/3b1...
github.com/Man...
All code for specific videos is visible here:
github.com/3b1...
The music is by Vincent Rubinetti.
www.vincentrub...
vincerubinetti...
open.spotify.c...
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[@SteveMould]

Can't wait for the final video! As always, your animations add so much clarity.

[@berkekus7053]

Comment under steve mould for sale

[@GooogleGoglee]

❤

[@didodido883]

They do.

[@d.mort.]

Hey Steve, Dave here. I think a wonderful follow up to this video would be about why the polarizers in this video are in the wrong direction and the reasons behind the common misconception. I am an electrical engineer with a passion for light, I would be happy to collaborate!

[@gregorywitcher5618]

*helically twisted* clarity, my favorite.

[@aSpyIntheHaus]

Holy Moley! This has Dunning Krueger'd me (You don't know, what you didn't know but we're confident that what you knew was sufficient until you learn something new) in such a wonderful way.

[@ashtag4043]

Man I wish I had your voice. Great video as always!

[@justinahole336]

Well, now I know what I'm doing this long weekend with my kids! Cool!

[@timp2751]

Well you spoilered the question with both the thumbnail and the animation at 1:04 so now I can never know if I could have known the answer if asked! 🙂 One of those things that seemed simultaneously 'wow' but also immediately obvious just from the thumbnail showing the answer.

[@GabrielPettier]

2:41 i half expected the colors in the tube to also move when moving the *other* filter, and i'm relieved, things are not yet incredibly weird, just, normal quantum weird.

[@Mystikan]

You need to use a full-spectrum light source, such as an incandescent, halogen or fluorescent lamp for this experiment if you want to replicate these results. If you use "white" LED lamps, you won't get all the colours; you will see only only alternating stripes of yellow and blue. This is because LEDs only output monochromatic light, that is, light of a particular primary colour. Most "white" LEDS work by having two emitters, one yellow and one blue. The combination of these two opposite colours fools our eyes into thinking we are seeing white light. If you use "colour-changing" LED lamps - the ones that come with controls that allow you to change what colour they emit - you'll see three stripes in this setup; red, green and blue, which are the three primary colours they combine to create the effect of all other colours. For example, what you see as pink or purple is actually a combination of red and blue with no green. As you change the LED lamp's colour setting, you'll see the three stripes brightening and dimming according to their composition of the colour you've set the lamp to.

[@ryuail]

With my very basic understanding of light in a medium I'm going to guess the color bands on the side of the tube are formed from the slight reflections of the light waves as they pass through the sugar crystals within the solution. Some amount of the light being redirected. Not too sure on the cause for it being diagonal, certainly to do with the polarization of the light though not sure what causes the "spin".

[@krisrhodes5180]

Me: What exactly is wiggling, and what is the significance of wiggling in a direction? He: Don't worry, we're going to go much deeper into what exactly is wiggling, and what the significance of wiggling a direction is. Me: I love you.

[@carultch]

It's the electric field that is wiggling. The electric field oscillates as light passes along region of space, in a direction perpendicular to the light's direction of travel. The magnetic field is involved as well, in a third perpendicular direction. Usually when people identify the polarization orientation of light, they are identifying it based on the orientation of the electric field oscillations. If the electric field is "surfing" in the z-direction as the wave propagates in the x-direction, then the magnetic field will be "snaking" in the negative y-direction. There is right hand rule that sets up the relative directions, where the index finger points with the electric field, the middle finger points with the magnetic field, and the thumb points in the direction the wave is travelling.

[@krisrhodes5180]

@@carultch You can desist, 3b1b already has my heart.

[@sietuuba]

Isn't that neat! A fascinating sight.

[@Rationalific]

Amazing stuff. It seems there's always more out there to discover! Thanks for helping to explain this topic! But I also have another question... Why, even with sucrose being chiral, does it all turn in one direction and not the other, or balance out? The molecules, by their very shape (no matter which way they are facing), can only make the light "turn" clockwise based on the point of view of the light source, right?

[@mrjxn007]

What would sugar water look like if it were sprayed as a mist with sunlight? (Compared to a typical rainbow in regular water droplets)

[@dl5244]

THIS is how science begins!

[@GordonHugenay]

All of physics should be taught by mathematicians. It's just so much clearer.

[@Epiminide]

Fun fact: Measuring the angle between the two filters can provide an estimation of the amount of sugar in the solution. This trick is applied to precisely evaluate the amount of sugar in wine grapes and must. These animations are awesome!

[@seth094978]

Is that the brix percentage?

[@Epiminide]

@@seth094978 I think Brix measurement is based on refraction properties rather than polarization. But I am far from being an expert in this field.. Let's wait if someone can clarify this point..

[@rafael_l0321]

@@seth094978 He is refering to a polarimeter, which uses a specific light frequency (to avoid the phenomenon shown in the video). As far as I know, °Brix (degrees, not %) is usually measured with a refractometer, but you can convert the concentration measured with a polarimeter to °Brix

[@ricgreen1]

Could we use this technique create a non invasive glucose monitor for diabetics?

[@amruthchangappa]

@@ricgreen1 I don't think so, you would still need a blood sample for the polarimeter, and blood has many other substances in it that would prevent this from working.

[@ricardopinho630]

every video of this guy is a phd paper

[@PowerhouseCell]

Love to see Grant branching out. He's truly made an impact on all online education, not just math! ❤

[@hanknew9685]

Omg yes this is getting into chemistry and enantiomers! Super excited to hear the math behind this

[@TheNameOfJesus]

The universe is made with complex math, so his expertise will be amazing if he breaks into physics and similar subjects.

[@theodorekim2148]

@PowerhouseCell Wait you're the guy who makes biology videos with Manim! Love your channel!

[@arvinderbali]

Basically, maths is behind all, so u understand math, u understand all.

[@TheNameOfJesus]

@@arvinderbali Maybe, but "maths" has been proven by Godel to be "incomplete" and therefore it seems unlikely that the universe is "incomplete." So there must be more to the universe than "maths."

[@cdenn016]

I've studied light/matter interactions for 20 years, published papers and such, and had never seen this before. I was pleasantly surprised! I wouldn't have thought you'd see light via the side. How great The more you learn the more you realize you know next to NOTHING

[@glenfoxh]

Gene Simmons from Kiss said next to the same thing about women. The more you think you know about women, the less you really know. And that is one guy, who has likely been with a lot of different women in his life.

[@91722854]

do you mind sharing what your research is in and your link on google scholar? I do research in optics

[@paveltroev8221]

the lamp is set off the axis

[@Eric-xh9ee]

I did research in optics. This should be obvious to you if this was your profession.

[@quinnphys]

Hey folks, Quinn here. Lots of people have been asking how they can make this demo themselves, so here’s how I built it: Materials: ⁃ Table sugar (sucrose) ⁃ Water ⁃ A glass tube that you can fill and seal, although it would be cool to experiment with different materials for the tube, since different material = different index of refraction. More on this in part 3 of the video. The tube should be long enough so that you can actually see the effect from the sides - our tube is 1 meter long, but you’d probably be able to see the effect with a ~0.5m tube. You also might want to make sure the tube is easy to open so you can clean it. See “Things to consider” for more. For the mini-demo, I just used a drinking glass! [FYI, the tube in this demo was custom-made for the MIT Physics Department. I’m not sure exactly where it came from or what type of glass it is exactly…] ⁃ A source of white, unpolarized light. We used a Dedo lamp, and if you make the demo as big as we did, you need a pretty powerful light source. For the mini-demo, I used my phone’s flashlight! ⁃ Two linear polarizing filters. You can get ‘em online pretty easily! Directions: ⁃ For our demo, we made a sugar solution of 300g of sugar per 400g of water. So, you should measure the volume of your tube and scale this ratio accordingly. ⁃ Boil the water and mix in the sugar until it’s dissolved. ⁃ Let the solution cool, then fill the tube with solution. Close up the tube. ⁃ Place the light source so it’s shining down the length of the tube, then place a filter between the light and the tube. ⁃ Place the other filter at the end of the tube. ⁃ Voila! You can rotate the first filter to see the whole spiral move up and down the tube, or you can rotate the last filter to see the color coming out of the end of the tube (and through the last filter) change. Things to consider: ⁃ You really want the tube to be clean before you start, since the solution can get moldy. If you look up close, you’ll actually see little floating things in the solution - those are some bacterial friends :) ⁃ We try to replace the sugar solution frequently so that the demo is clearer. ⁃ The shorter the tube is, the more concentrated you want the sugar solution to be in order to see a similar effect. ⁃ The amount of rotation of the polarization angle is proportional to the concentration of the solution (this is called the specific rotation!) ⁃ The light might get hot the longer you keep it on, so be careful! As always, observe sensible safety procedures. ⁃ You could do this with different sugars! Glucose would also rotate light to the right, but slightly less than sucrose. Fructose rotates light to the left! If you recreate this/do something else cool with it, I’d love to see!

[@Pranshu_Agrawal]

Only 47 Likes and no replies? Thanks for this and for taking the time to build this!

[@kredibled]

It’s likely borosilicate glass, most scientific glass is. You’re likely able to find a local glass blower who could make the fillable tube but the caps might require some thought. Could just superglue a small glass plate to the ends 🤔

[@Arc125]

Ordered filters to try this at home!

[@R23874]

Quinn, thank you so much for what you've built here. I greatly enjoyed this video, and it has rekindled my interest in studying optics.

[@Crushnaut]

Is LED light on your phone actually white light? When you split it, do you end up with the three specific wavelengths of light corresponding to wavelengths from each LED making up the white light? Either way, I think that would be a cool follow up to this. Use different light sources and see the effect. If you did use three wavelengths (rgb), how sharp would the drop from one colour to the next be? Would you get twisted lines around the tube for each colour or would there be areas dominated by each colour with gradient transitions?

[@Nighthawkinlight]

What a beautiful demo setup!

[@pierrefrebet5630]

Hello @Nighthawkinlight ! Love your channel !

[@tachoblade2071]

This is like being at the center of the research table of grant, listening to the ideas and just absolutely loving your time learning. This is exactly what college/higher education needs to be, collaborative on a world level. Ofcourse, i am only a viewer and not a collaborator, but it just feels insanely amazing to be able to listen to this information

[@TheArizus]

I 100% agree. As someone who's experienced maths olympiad camps my favourite part is the collaboration.

[@imad8903]

me too @@TheArizus

[@ManuelBTC21]

A landmark in science communication. Thank you and congratulations.

[@z0nx]

Just some lads making videos.......................................................................................................................... !

[@3blue1brown]

Part 2 is available now: kzbin.info/www/bejne/l4m1hZawdrOof9Usi=m6DgY1ogMrwTRrUP Some viewers have asked about how to make this demo for themselves, and Quinn kindly wrote up the description below. Materials: ⁃ Table sugar (sucrose) ⁃ Water ⁃ A glass tube that you can fill and seal, although it would be cool to experiment with different materials for the tube, since different material = different index of refraction. More on this in part 3 of the video. The tube should be long enough so that you can actually see the effect from the sides - our tube is 1 meter long, but you’d probably be able to see the effect with a ~0.5m tube. You also might want to make sure the tube is easy to open so you can clean it. See “Things to consider” for more. For the mini-demo, I just used a drinking glass! [FYI, the tube in this demo was custom-made for the MIT Physics Department. I’m not sure exactly where it came from or what type of glass it is exactly…] ⁃ A source of white, unpolarized light. We used a Dedo lamp, and if you make the demo as big as we did, you need a pretty powerful light source. For the mini-demo, I used my phone’s flashlight! ⁃ Two linear polarizing filters. You can get ‘em online pretty easily! Directions: ⁃ For our demo, we made a sugar solution of 300g of sugar per 400g of water. So, you should measure the volume of your tube and scale this ratio accordingly. ⁃ Boil the water and mix in the sugar until it’s dissolved. ⁃ Let the solution cool, then fill the tube with solution. Close up the tube. ⁃ Place the light source so it’s shining down the length of the tube, then place a filter between the light and the tube. ⁃ Place the other filter at the end of the tube. ⁃ Voila! You can rotate the first filter to see the whole spiral move up and down the tube, or you can rotate the last filter to see the color coming out of the end of the tube change. Things to consider: ⁃ You really want the tube to be clean before you start, since the solution can get moldy. If you look up close, you’ll actually see little floating things in the solution - those are some bacterial friends :) ⁃ We try to replace the sugar solution frequently so that the demo is clearer. ⁃ The shorter the tube is, the more concentrated you want the sugar solution to be in order to see a similar effect. ⁃ The amount of rotation of the polarization angle is proportional to the concentration of the solution (this is called the specific rotation!) ⁃ The light might get hot the longer you keep it on, so be careful! As always, observe sensible safety procedures. ⁃ You could do this with different sugars! Glucose would also rotate light to the right, but slightly less than sucrose. Fructose rotates light to the left!

[@GooogleGoglee]

❤

[@richardsmith3021]

You should pin this.

[@d.mort.]

Hey there, I have a fundamental correction to the visuals in this video. The polarizing filters are oriented incorrectly. When the polarizer is vertical, it will transmit horizontal and reflect vertical. It’s a common misconception, if you would like to hear more I would be happy to share! (I am an electrical engineer with a passion for light haha) PS these are some amazing quality videos!

[@MatthiasBussonnier]

+1 to this, it's hard to test with visible light polarizers, but you can find educational material that does it with ~10cm wavelength. The idea is that the electrons can move in the direction of the line filter can move sufficiently along this direction that the dissipate the energy of the light polarized in the same direction right ?

[@GooogleGoglee]

@@MatthiasBussonnier but please, fix your English first, I am not understanding what you are asking exactly

[@neiljudell1437]

I first saw this in 1973, in Walter Lewin's class on vibrations & waves at MIT. Damn, he was a great lecturer.

[@krissp8712]

True, and yet as great as he was, Lewin still turned out to be misusing his role like a creep in the end.

[@أحمدالدسوقي-ت9س]

Lewin is the best❤❤

[@itishappy]

I'm an optical engineer. I have solid intuitions about light. I still said "what?!" out-loud involuntarily when the lights dropped the first time. What an amazing video!

[@Serizon_]

it truly is an amazing video

[@userJohnSmith]

Right there with you (optical and opto-mechanical) the angle is weird. You just don't anticipate the "rotation" to be so slow...

[@KeithSmith42]

Any chance this will replace separate RGB diodes someday?

[@userJohnSmith]

@@KeithSmith42 Diodes replaced this actually. It's how LCD screens work.

[@KeithSmith42]

@@userJohnSmith So before RGB pixels were single tubes that used a filter to output the desired wavelength? I thought diodes replaced electron gun-based CRT screens

[@rex-up9ln]

Im a chemist. the dependence of angle of polarization by a chiral molecule on frequency of light is a very useful phenomenon which gives rise to cotton effect. Different molecules and even parts of a molecule have a different signature and thus the plot of angular dispersion vs. freq can help identify a molecule and functional or structural motifs. See Circular Dichorism spectroscopy

[@ENCHANTMEN_]

How does the chirality cause the twisting even though the molecules might be in any orientation? My intuition would be ones facing the opposite direction cause it to twist the opposite way, but clearly that's not the case here

[@tomc.5704]

@@ENCHANTMEN_ I'd love to know too -- I don't have the intuition for this at all. I'm trying to use my hands to represent chirality / circular polarization, with my thumbs representing the direction of travel and the curl of my fingers as the twist. It seems to make sense -- if you had an equal number of left hand and right hand chiral sugars (represented as both right and left hands with the thumbs pointing in the same direction) then the twist would cancel out. But it's also really easy to get the direction of twist to cancel out with one hand. Just turn your thumb to point the other direction. So what's different about pointing your hand in the opposite direction, and light hitting the sugar molecule from a different angle (ie the opposite side)?

[@MarkFord-k4z]

@@ENCHANTMEN_ The light does not just interact with a single molecule, so you can consider an average of all the molecules that the light interacts with being equivalent to averaging one molecule over all orientations. A chiral molecule averaged over all orientations cannot be superimposed a similar average for the other enantiomer - essentially the average is still chiral. Plane polarised light can be equivalently described as a balanced sum of right and left helically polarised light. The sample will interact differently with right and left helically (circularly) polarised light, which leads to the twist in the polarisation plane.

[@cactuskiller3558]

Like for "Essence of topology"

[@shayantanmukherjee243]

Sometimes, I wish I could just stay with Grant. I could do all his household chores, any work he would ask for and in return I would just learn from him, ponder about various questions in the universe, that's it and I'm just a happy man in this lifetime.....

[@lotofAlexa1221]

Quantum physics lets go

[@geekjokes8458]

well, ultimately it should be explained by quantum mechanics but i think classical EM would be able to solve this or maybe it's necessary for the 3rd question, idk

[@dilation1057]

I don’t think quantum mechanics is REALLY required at a deep level most concepts such as chirality, refraction and polarisation can generally can be solved using the wave theory of light but for the third question i really doubt only optics can help. Overall speaking this problem really does some need of quantum mechanics.

[@iddomargalit-friedman3897]

I think classical EM is probably enough here

[@shrill8239]

​​@@geekjokes8458I am thinking it much more related to the optical properties of the material in consideration.... idk too?😅

[@stevenfallinge7149]

Not everything is quantum magic/woo/mystery or blah blah blah.* Too many people think "quantum" and start thinking like it's magic instead of actual science. *(of course, technically everything is quantum, a detail many also miss)

[@lesconrads]

The visualisations is on another level. I am incredibly impressed by how you can create these moving 3D animations to show super complicated concepts.

[@ManishaPatel-sl8dp]

This is a phenomenon occurring due to optical activity of sugar. Known as optical isomerism. If a compound is optically active , it will bend light to a certain degree. I don’t know why this wasn’t mentioned in the video.

[@pythonboi5816]

Guys look a multi colored LED

[@2Sor2Fig]

I remember learning about chirality in Chemistry 201. Most of the time I'm mostly along for the ride, but today it did feel intuitive. Learning from you has completely changed my view of mathematics, and I thank you for that.

[@TheArizus]

A day with a 3blue1brown video is always great but a day with 2 uploads is exceptional!

[@AlphaPhoenixChannel]

yup - i'm hooked. I was torn between some kind of stress-in-the-glass-polarization, something having to do with polarization dependent reflection, and a vague un-thought-out concept of polarized scattering like the dark band 90 degrees from the sun... sounds like it's the third and i should think harder! can't wait to see the rest. In retrospect those first two don't work at all because the polarized twisting light is only traveling axially... until it scatters... hmmm...

[@AlphaPhoenixChannel]

oh shoot wait both parts out at once??? sweet

[@aozorakei5288]

First

[@gallium-gonzollium]

My feeling for question 3 could be due to the tube acting like a prism, scattering different light at slightly different directions, magnified by the lens effect of the cylindrical tube.

[@PhilBoswell]

Subtitle nitpick at 6:04: s/weekly/weakly/ Very much looking forward to the next video 👍

[@PhysicswithElliot]

My jaw dropped when the spiral rainbow appeared. So freakin cool!

[@claaaaams]

This is such a great video with the way it's setting up other discussions. Thank you for making physics accessible!!!

[@bandana_girl6507]

Having played around with a lot of polarizing filters and looked through a ton of information about how it works with scattering, I have built up an intuition, and I am really excited to see how you make it easier to understand.

[@zalibecquerel3463]

I barely understand this, but am very interested in something: The concept of "invert sugar". Home brewers sometimes will make this (you boil sucrose in a slightly acidic solution). All I know is that this has something to do with chirality, and that it can measured with a refractometer. If we were to fill the tube with "invert sugar", would the angle of the stripes change? And to what angle would the change be? 180 degrees? Something else?

[@aryasaktiflister_aw]

I came to this video as someone who only vaguely remembers some HS optical physics so I didn't expect to be too intrigued. Instead, that animation and explanation moved mo to the verge of tears. So beautiful and curiosity-enabling

[@Taxodium-d2j]

Grant is trying something new, adding a bit of physics experiments to the recipe! Glad to see that the channel is looking towards a bit of variety. Not that the usual maths animations were bad, they were exceptional as ever, but this is great to exploit the viz towards more intertwined maths and physics, I love it. Keep it up, Grant!

[@primenumberbuster404]

Steve Mould and Grant Sanderson has the best therapy voice of all time. ;)

[@matheusrossetto5091]

I saw this video as one of the great documents some immense scientist from the 19th century left as his legacy. What youre doing is just incredible, a friend of mine and I literally chose our graduation courses (Mathematics for him, Mech. Eng. for me), greatly thanks to your influence during our high school. Thank you for your ridiculously amazing work!

[@Inspirator_AG112]

This is the first physics video I have seen from this channel.

[@gradientO]

3b1b physics videos are a delight to see

[@Erosis]

Holy mother of god this is great! Optics was one of my weakest subjects in physics. It felt like a lot of it was just "this is how it is." I'm so excited to follow this series. I feel embarrassed, though, that as someone with a degree in chemistry that I didn't even consider the chirality of the sugar. I've used polarimeters in lab! Duh!

[@logenninefinger3420]

Very nice topic! When Math meets Physics, things get interesting :)

[@brainxyz]

Short wavelengths (blue) are slowed more sharply upon entering the sugar solution than are long wavelengths (red) due to the different refractive index, hence, colors look separated from the side of the tube.

[@carultch]

Could a material ever exist that has a uniform refractive index as a function of frequency? My name for such a material property, is isohertzic.

[@Roanmonster]

I am very much using this video in my classes, and my heart jumped a little when I saw you could do the demo yourself! We are adding optics back into our curriculum (highschool physics) and this will be so interesting to see

[@dubscheckum8246]

This is way beyond any highschool or AP course

[@DrDeuteron]

0:18 Your linear polarizing filter has a little arrow (vector: direction, Y_(1, m )) showing the filter's alignment. It should be a double headed arrow b/c linear polarization is a tensor alignment (no direction, Y_(2, +/-2))

[@BlueRaja]

9:45 "Our brains do something to make rainbows more vibrant than they really are" - actually it's because RGB isn't able to accurately represent intense colors. Only something like a third of the full human-vision chromaticity diagram can be represented using RGB.

[@davekwcc]

You have such a gift at explaining complicated subjects in interesting and engaging ways. Thanks for another excellent video!

[@nirajandata]

finally after long time

[@tricanico]

classic 1000% likes to views ratio right now

[@TesserId]

Ooooooooh, the colors. No, seriously; it's really beautiful.

[@d.lawrencemiller5755]

I was guessing that the curvature of the pipe has something to do with the diagonal stripes. I was wondering if it would look different in a square tube. Looking forward to understanding the rest of this video series so I can make a hypothesis about what a square tube full of syrup would look like

[@TeaDrinkingGuy]

I have never seen this phenomenon before, which is a surprise because I love Steve’s videos. What a beautiful phenomenon that’s quite easy to replicate! Seeing this in science class as a kid would have seemed like magic.

[@erics3367]

The color is something I haven't seen before. In physical chemistry we used the polarization to measure the concentration of the sugar with monochromatic light. In a way where we used the second folter after the tube and turned it to an angle where no light passed though, that gave us the angle the light turned and the concentration. ps we did this with sucrose which splits into fructose and glucose, inverted sugar, because it changes the angle. sp we measured the change of the angle to find the speed of the reaction. Would be interesting to see if this also affects the colors. My thesis would be, starting from sucrose, you would see the spiral slowly unwinding and then winding up in the other direction

[@worldhaseverything]

Thanks for lighting me to this new knowledge.

[@sainadh7]

Beautiful experiment. As someone who worked in spectroscopy with chiral molecules, I must say this is a must demonstration in graduate classrooms. The experiment has refravtive index, polarisations, optical rotation due to chiral molecules, all playing their role simultaneously.

[@HomieSeal]

Oh nice, glad to see a new 3B1B video!

[@iainmackenzieUK]

I am a British Physics teacher working in China. I really appreciate the questions you ask and how you ask them/ explore ways of answering. gets to the core of what we are trying to encourage in our students. Great work

[@Ninjaeule97]

What made you move to China and work there?

[@李某-c6h]

I just learned about optical isomerism in A-level chemistry, and I'm not sure if it's related to this video.

[@iainmackenzieUK]

@@Ninjaeule97 The question really is "why would I ever move back?" :) Lovely students, interesting culture, many varied daily challenges, the money is pretty good.

[@iainmackenzieUK]

@@李某-c6h from what I recall of my chem I think it is very much linked...

[@Ninjaeule97]

@@iainmackenzieUK Glad that you enjoy your life there. I just haven't heared of many westerns move to Asia and choose China instead of one of the more democratic (and wealthier) countries in that region. So I had to ask.

[@diomedesabcmnxyz7299]

~ I would say that a good explanation of wiggling would have to do with the two component properties necessary for light propagation, transverse & perpendicular waves. The single direction polarizing filters are the main facilitators in distinctly separating these two component properites. ~ Sugar water's optic reflexes which include it's index of refraction, reflection, & diffraction properties also attribute to this interesting phenomena, since sugar water is a homogenous solution. ~ The separation of colors thus barber pole wiggle effect is due to the unique wavelength & frequency of each monocolored light source having it's own inherent transverse & perpendicular properties.

[@d.mort.]

I can’t find my old correction so I am reposting it here: Hey there, I have a fundamental correction to the visuals in this video. The polarizing filters are oriented incorrectly. When the polarizer is vertical, it will transmit horizontal and reflect vertical. It’s a common misconception, if you would like to hear more I would be happy to share! (I am an electrical engineer with a passion for light haha) PS these are some amazing quality videos! Edit 1 for clarification: An experiment I performed in undergrad involved a square with equally spaced vertical wires. We placed it between a transmitter and receiver (transmitting vertically polarized EM waves, maybe 3GHz but I don’t recall). When the wires aligned with the direction of polarization, the receiver signal dropped drastically and vice versa.

[@TheGreatAtario]

Isn't this just labeling the same thing with a different word?

[@ghislainbugnicourt3709]

That's interesting ! A quick convincing argument is that when the electrical field oscillates along the stripes it induces currents so the light is reflected like on a metal. If a polarizer has an arrow, what's the convention then ? Should it show the orientation of stripes or the polarization you obtain ?

[@d.mort.]

The arrow is a good indicator. I would say a vertical arrow to denote the direction it allows to pass through, but the lines should be perpendicular to that arrow. An experiment I did in undergrad involved a square with equally spaced vertical wires. We placed it between a transmitter and receiver (transmitting vertically polarized EM waves, maybe 3GHz but I don’t recall). When the wires aligned with the direction of polarization, the receiver signal dropped drastically and vice versa.

[@The_Canonical_Ensemble]

Who said that the vertical lines on the polarizers represented the orientation of the wires?

[@ghislainbugnicourt3709]

@@The_Canonical_Ensemble Well, that's how we perceived it at least. If I see a drawing of, say, a fence with vertical lines I'm not gonna guess that the physical planks they represent are horizontal.

[@rjkirkland8659]

This is better than Christmas...I love these very tangible, available examples of the complexity in the world and how it leads to fascinating experiences.

[@stevepittman3770]

1:48 Ok, now I want a floor lamp filled with sugar water with a slowly rotating polarizing filter. Also I wonder what this would look like if you mirrored the far end so none of the light escapes out the top - would the light twist back to the original orientation and cancel out the apparent spiral of colors?

[@andrewharrison8436]

Yes please! As to your question - interesting - it would obviously make things brighter! I think each colour could be regarded as a bolt thread with a different pitch. Then the mirror would send each colour back down the same thread. It would then reassemble to one polarisation at the lamp end.

[@timp2751]

The light will continue to twist in the same direction (relative to direction of travel) so more likely to end up with a pattern of sort of rhombusy nature as the returning light and outbound light contribute different imbalanced spectra to what eventually makes it out of the side of the tube at any point

[@T3sl4]

I'm holding up a polarizing filter to this video and it's just going normal and dark, what gives?! /s Silliness aside, wouldn't that be cool, to be able to take full polarized or even phased optical images? In full color and video, even? Well, that just describes holograms, doesn't it. :) At least, for some degree of complexity; full color is even less trivial, of course. Heh, yikes, imagine the bitrate on holographic video...

[@HeisenbergFam]

Didnt expect to see Blue's upload right on the start of September, cant wait to see another next month or in 2 months..

[@RubixB0y]

Comes across kinda passive-aggressive when there hasn't even been enough time to watch the video before posting that comment. I appreciate every video whenever it comes out because he puts quality first.

[@SilverBullet93GT]

That would make an amazing barbershop sign, yes folks, you heard it here first, waiting for my 10% :)

[@AnExPor]

Yahhhh! Don't always like a cliffhanger but in this case, it means more 3B1B videos. Can't wait!

[@160p2GHz]

As a polarimetrist-- this is so great! I'm so exited for these videos. You and Steve Mould are my favourite STEM communicators (and not just because you have both covered polarization multiple times). So exited for this series (And thanks to Quinn for coming up with this!)

[@siddhantkumar6340]

The more I see 3blue1brown, the more angry I am at the school curriculum for not teaching us this gold. It is sort of like an axial dispersion of white light.

[@taiconan8857]

QUINN BRODSKY DESERVES MAJOR PROPS! *What* an idea and solid execution of said demo! We likely wouldn't have had this video *without* her perspective. Thank you for returning to this in *force* 3B1B! And including Steve Mould was just icing on the cake~ 💎

[@Dangerdad137]

Brewster's angle! That is, the same reason a polarized filter on your sunglasses will make reflections off puddles go away while driving. If the transverse wave of a given color aligns with your plane of vision, you won't be able to see that color, so I think the view from the side is those transverse waves aligning with our plane of vision, so that's what gives rise to the different colors.

[@julianwalford]

Wow! I’ve loved your videos for quite some time, @3blue1brown, but I’ve never felt so excited as just now seeing this teaser. I did a PhD and postdoc in optics 20 years ago, in areas very close what you’ve shown here. This is the clearest and most beautiful video I’ve seen on this topic and I am already learning something I didn’t know before. Thank you so much for everything that you for maths and physics education around the globe!

[@UddiptaKalita-il2vh]

Please please make a course on Tensors for Bigginers..

[@bryanchaves5691]

Great content. Keep up the insane work 😊

[@Dudleymiddleton]

What do you mean "Insane"? Do you actually know what that fucking word means? I am sick to the teeth of seeing and hearing it everywhere. Mental illness is a very serious subject and this is extremely offensive.

[@kfftfuftur]

When light is reflected / transmitted through a dielectric surface, the reflected and refracted light has different polarization. Specifically if the incidence angle happens to be the Brewster angle the difference in polarization is maximal. My guess is that because the ratio of reflection and transmission depends on the polarization of light, a polarized photon leaving the tube is more or less likely to be reflected on the surface of the tube depending on the polarization angle. So what we see when we look at the tube is that light will initially mainly leave the tube to the top and the bottom, but as the polarization the direction of the direction of the light leaving also changes.

[@Lolwutdesu9000]

Just a small point to raise: linear polarisers actually allow light that is NOT parallel to the chains present in the polariser material, usually denoted as the straight lines drawn on a linear polariser. So if the polariser wants to allow vertically polarised light through, the lines should be aligned horizontally. I know it's a small menial detail, but it is important, as it can invoke incorrect assumptions about how light is polarised in the first place.

[@kumarquanta]

will the diagonal direction be different(anti-diagonal) if the solution is replaced with its chiral counterpart? I assume the molecule rotates the polarization direction in one way and its chiral counterpart rotates in the other way so that you end up with different diagonals. this is my guess may be I am wrong

[@TesserId]

If Icelandic spar calcite creates birefringence, which splits perpendicular polarizations into two refraction images, then shall we call this spiral chromatic polyfringence?

[@neoh524]

Higher frequency light has a higher capacitance. The medium changes the rate of induction for each frequency acting as a prism. The helical structure is represented by the right-hand rule

[@erdngtn9942]

So the whole “chirality” ideas in Death Stranding are making both less and more sense as I learn more about it.

[@pamaramb]

I insist. This guy deserves the Nobel Prize in Education. And given that it doesn't exist, he also deserves it to be created.

[@BigUrta]

dawgs like “why anything?” and im like damn mf i dont know, im just tryna learn here 😭

[@borisbukalov9407]

Awesome! I didn't know you make physics videos. This is as good as your math videos! Keep up the great work!

[@dr.python]

The violet light would travel to the future in that case, or experience time more slowly than red light.

[@bungalowjuice7225]

Pff, the light rays are obviously happy to tast sugar and thus are doing pirouettes.

[@1337treats]

I wonder how the tube would look if you passed the source light through three 45° filters. That’s where some quantum magic happens that allows light through three but not two filters.

[@padhlekyakarrhahaituyahanp1011]

I read this in 12th in chemistry of as optically active compund (chirality etc ) didn't learns about why great video😊

[@danielsoundso855]

You can use a white cell phone screen instead of a light source plus a polarizing filter.

[@AnitaSV]

5:58 proportional to square of the component. So that cos^2+ sin^2= 1

[@AdmiringAlligator-kf4vj]

If tube is so long is it possible this different colours light combin again

[@niks1632]

What is expected for brown sugar, dextrose instead of white sugar?

[@EDToasty]

i swear i'm going crazy, when i saw this video yesterday, the thumbnail was mirrored

[@DiThi]

I want to try the same experiment but with a purely monochromatic light.

[@himselfe]

My thought through most of this video was "this could be used to make 'true' colour LCD displays", probably need a medium other than sugar water though.

[@dl5244]

very cool idea to share! on or about Sep 7 2023, the prior art for the idea and concept of controlled twisting of light to create a 'true' color display (LCD or otherwise) was made public (no known patent pending)!

[@ntq1ty]

I love how attentive and interested the cat is that's watching the home experiment at 6:45 😻