3Blue1Brown - 2023-09-01
Explaining the barber pole effect from the last video: https://youtu.be/QCX62YJCmGk Next video on the index of refraction: https://youtu.be/KTzGBJPuJwM Help fund future projects: https://www.patreon.com/3blue1brown An equally valuable form of support is to simply share the videos. Timestamps: 0:00 - Recap 0:44 - The radiation law 6:10 - Simulating the radiation law 11:11 - Why the diagonal stripes? 16:31 - Why does it twist? Thanks to these viewers for their contributions to translations Hebrew: Omer Tuchfeld Indonesian: akhyarr ------------------ These animations are largely made using a custom Python library, manim. See the FAQ comments here: https://3b1b.co/faq#manim https://github.com/3b1b/manim https://github.com/ManimCommunity/manim/ All code for specific videos is visible here: https://github.com/3b1b/videos/ The music is by Vincent Rubinetti. https://www.vincentrubinetti.com https://vincerubinetti.bandcamp.com/album/the-music-of-3blue1brown https://open.spotify.com/album/1dVyjwS8FBqXhRunaG5W5u ------------------ 3blue1brown is a channel about animating math, in all senses of the word animate. If you're reading the bottom of a video description, I'm guessing you're more interested than the average viewer in lessons here. It would mean a lot to me if you chose to stay up to date on new ones, either by subscribing here on YouTube or otherwise following on whichever platform below you check most regularly. Mailing list: https://3blue1brown.substack.com Twitter: https://twitter.com/3blue1brown Instagram: https://www.instagram.com/3blue1brown Reddit: https://www.reddit.com/r/3blue1brown Facebook: https://www.facebook.com/3blue1brown Patreon: https://patreon.com/3blue1brown Website: https://www.3blue1brown.com
Nothing makes me happier than seeing part 2 uploaded less than half an hour after part 1.
But then another twenty minutes later we discover it's still a cliffhanger!
3B1B trying not to edge his audience challenge (Impossible)
I couldn't watch the first video immediately so at first glance when the second notification came I honestly thought it was the same video but he changed the title and thumbnail slightly to trick the algorithm into giving him more views.
Being prepared for sucess
Yaeeeesssss!
Fun fact: The charge wiggling in the z-direction is called dipole radiation, and it's what antennas use. The drop to zero in the z-direction is why you actually get very poor cell reception when you're directly under a cell tower.
Oh my god, that makes so much sense. Does that mean anything that radiates any kind of signal will do this exact thing?
@@__Random_user_ I wouldnt say anything, because then we wouldnt specify that it's dipole radiation. But certainly a lot of things do
@@allanjmcpherson Yeah I guess so. Also what was the answer to the last question? I don't think he answered it in the video nor comments or I'm blind. The sugar slows down rotation to the right more?
@@__Random_user_ I could be wrong, I have not seen their answer, but I think the answer is that it slows down light rotating "left" i.e. counterclockwise looking down the tube from the light source. We can tell from the diagonals that the polarization of the light is being rotated clockwise, thus the counterclockwise bit must have been slowed down
@@jackbeda521 I may be not understanding the effect but looking at e.g. the thumbnail and picking out let's say the color blue it creates a counter-clockwise spiral. Doesn't that mean the rotation to the right is slowed down?
This should be nominated for a communication prize. A winning video. Bravo.
deadass bruh. Explained everything highschool physics refused to elaborate on.
In organic chemistry, we learned that you can measure how much the polarized light "rotates" to determine the ratio of left handed to right handed chiral molecules in a racemic mixture. What's surprising, and beautiful, is that this effect is visible on such a length scale. Each full twist is a significant fraction of a meter in length, rather than being microns in length, so it's actually visible and really easy to see!
I thought similarly about the length we see here, but in the opposite end; It could well also have needed really large distances.
One thing that was most surprising to me (I guess because I have a Physics PhD but know almost nothing about organic chemistry) is that there would be enough of an imbalance in the chirality of the sugar molecules to see this effect. Naively, I expect nature to not have a strong chiral/parity preference (except for neutrinos) so if you grab a handful of sugar I'd expect roughly 50/50 mix of handedness. But apparently what you actually get with sugar (and lots of other stuff) is a strong preference for one chirality over the other.
@@Anytus2007 Invert sugar is easily available... I'm assuming the color spiral would reverse if used here, but obviously just a guess.
@@Anytus2007 I don't have a chemistry degree, but from my understanding, most of the simple biological molecules, including the simple sugars and amino acids are chiral. All simple sugars are naturally in the D-configuration and all chiral amino acids are in the L-configuration. The inverse configurations do not exist in living things at all. Apparently you can eat L-glucose, it tastes exactly the same as D-glucose, and is nontoxic, but it can't be metabolized.
So "reverse polarized sugar" does exist, but it needs to be made synthetically.
Most chemical processes that would be done in a lab are not stereoselective, and would produce chiral molecules in a roughly 50/50 mix, but biological processes are very selective.
Since sugar and light interact this way, is this the basis for the quantum effect of photosynthesis?
FYI: this effect is used in GPS. The ionosphere rotates the polarization of the L-band signal (Faraday rotation). By transmitting circular polarized radio at 2 frequencies, L1 and L2, the difference in the delay can be used to find the total delay, and since GPS is based on timing, you need to know the travel time btw satellite and receiver.
Really nice timing with the video Scott Manley uploaded on how gps works.
That second channel is only available to the military, though, correct?
@@TheToric idk, they keep changing it. The GPS signal is sophisticated.
I feel quite happy that I can understand this comment after watching the video.
This is actually a different sort of effect. The presence of a chiral molecule causes something called optical activity, whereas Faraday rotation is caused by a magnetic field along the propagation direction of the light. Both cause circular birefringence, but they are different effects arising from different physics. (And they are distinguishable; optical isolators are built using the Faraday effect because of the way that light behaves when you send it back through the tube, whereas an optically active material would do the opposite of what you want in that situation.)
This is what finally made the concept of "light is a wave" click for me. No amount of time in my physics class would have done that. So cool!
I have no words to express my admiration for.your work. I have been styudying EM waves for more than 30 years and its th first time I know somebody that can show 3D/EM waves in with this level.of detail in such a clear way. This animations should be what a genius like Maxwell could imagine more than 100 years ago. Its hard to classify you as a simple professor, because all this stuff requiere a high level of artistic sense too...you are like modern matematician artist as Leonardo Davinci was 500 years ago.
I fully believe 3blue1brown to be in a similar direction of science to what Feynmann did to particle diagrams. Sure, 3b1b and Feynmann didn't actually necessarily come up with new answers to existing problems, but the way they can make everyone looking have an intuition for how current solutions work and maybe have new answers come because of it is just incredible! This is what makes for great teachers, and I hope it gets the recognition it deserves
Super agree, absolutely brilliant thinker, visualizer, teacher. We’re all really lucky to have Grant’s work to learn from and admire.
Frankly, there is not a single channel on this entire platform, that is a of a higher quality. Concise, rigorous, profound; broad and foundational. So most importantly: beautiful! Grant, you are a treasure.
And FUN!
It bugs me when people say things like this who have not seen every "single" channel on youtube. His videos are highly explanatory. That's their job.
As a fresh masters radioelectronics graduate, I wish our professors had animations like this.
Noone had animations like this, undergraduate students are lucky to have 3b1b explain the phenomena qualitatively so well.
@@InXLsisDeo His visualizations are top notch. Back in the day, you had to come up with them in your head to be a successful student.
Be the change you want to see, now you have the opportunity to make animations like this for your students :)
@babblebam Ahoj! Tebe bych tu nečekal :D
@@mastershooter64haha… you illustrate a very good point. People can wish for a million dollars if they wanted. They don’t realize just how much work one has to spend in order to make these kinds of videos. There’s a reason animators on YouTube do YouTube full-time. Asking for teachers to produce this kind of content, or replicate its quality on a regular basis is literally like asking a baby to swim at the Olympics.
For those interested in a textbook that explains all of this and more, the best one I know is "Absorption and Scattering of Light by Small Particles" by Bohren and Huffman. It goes in detail for example in the difference between circular vs linear birefringence and dichroism. Also it was the first source that thought me about the Ewald-Oseen theorem---that's the secret sauce to understand what the index of refraction really is.
I am an undergrad math-physics student that will go on to teach others. Having worked in Manim a bit I cannot fathom the amount of time/skill you had to employ in making this short video. Yet you have already surpassed most of my phisics teachers and I can finally see, that it is indeed possible to learn and teach these things without all the pain I had to endure. This is so much different from the explanations I had been given that I wouldn't even believe it was possible with this much elegance and apparent simplicity of this problem. I can only dream and pray that I will achieve this level of expertise in explaining concepts. You are really the best role model I could dream of and since I hope to be using Manim while teaching as well, I can only thank you for your huge effort you already did for us. You helped me see math and physics with the kind of passion and beauty I saw it before the hardships of university came. I hope this motivation will help me with my studies and that I will have the opportunity to pass this feeling onto my students in the future. You really are among the most brilliant minds in modern times, at least in the field of pedagogy. Hats off to you.
Wow, thanks for such kind words. I imagine your students are already very appreciative if you're putting this much thought and care into how you can make learniner easier for them.
@@3blue1brown Well I don't officially teach anyone yet, but I do hope you will be right. Thanks for the reply, I appreciate it!
I'd hope he can make good Manim animations, considering he invented the library.
Grant is a god among men.
@@3blue1brown have you ever considered partnering with (science) museums and/or VR companies to offer those animations in 3D? I dream of spatially interacting with those kinds of animation (e.g. the radiation law) to get an even more profound intuition (experentially) about what is happening.
Hardships in Uni?
The visualizations of the fields youve created are honestly astounding. I am a post-masters student with a specialty in Quantum Optics and it was just so nice to see this visualized this way. Sometimes the visual connection really just helps it all make more sense.
Yeah, same for me too. See my comment above. It’s stunning to see this phenomenon animated many years after conceptualizing from textbook diagrams.
Post-masters student..?
@@Namerson "Post" generally means "after", so this implies I have finished my masters.
@@bolognious2263 I know what the prefix means, but that isn't how you say it in English. The correct way that native speakers would describe your situation, would be: 'have/ing a masters'. Post-masters student implies you have both completed a master's and are a student.
@@Namerson Pedantic american?
Part 3: https://youtu.be/KTzGBJPuJwM
A few commenters have asked whether you'd see different angles for the diagonal stripes as you change the distance from the tube, as this explanation would imply. It's a good question! We actually did those measurements, where our expectation was for the diagonal angles to become more vertical as the camera moves away from the tube (i.e. there should be less variation in color as you scan your eyes from the top to the bottom). But, that's not what you see! If anything, the boundaries become more horizontal, in direct contradiction to what you'd predict from this explanation.
The tentative plan is to talk more about this in the following video because there's a nuance here that's actually related to indices of refraction. I believe what's going on here is that we need to incorporate the lensing effect of the tube. Even when you're standing far away, and the line of sight to the top of the tube is nearly parallel to the line of sight to the bottom, because of how those lines of sight will bend as they pass through the circular boundary of the glass and water, and they will no longer be nearly parallel as they enter the water itself.
So in effect, the explanation offered in this video is qualitatively correct, but to make quantitative predictions you need to add more detail.
So can you use a squared "tube"?
Ah, yes... that makes intuitive sense. Looking forward to Part 3!
See I was actually expecting lensing to be the main explanation, and was a bit blindsided (and pleasantly surprised) by the geometric explanation in this video
I would have expected the diagonal stripes to form due to the reflection/refraction on the inside of the glass tube. Light with different polarisation gets reflected more or refracted more, depending on the incidence angle of the light. Only light that gets refracted goes outside the tube.
It may be a good experiment to put a polarisation filter next to the side of the tube, to see what effect that has.
@@Megaemce now that is the mind of an experimentalist....or maybe a theorist. idk.
Something in my brain went click. Having experienced years of education, dozens of books, hundreds of videos in this general area, this video makes several fundamentals I've never understood just jump out. An outstanding piece of educational work. Thank you!
You are a math rockstar dude. This videos are the top cream educational content for ppl who don't want to smash their heads against books but still want insight. Thank you.
..and just as gifted of an educator. The gratitude I feel to enjoy his math videos, and free no less, is only slightly tempered by the wish to see content of this quality in other subjects. 😅
He makes it easy to keep up and understand. This topic could easily be made to put people to sleep.
Wow. This, and the part 1, are just mesmerizing to watch. Very well put together and just beautiful with the combination of the footage from the setup and the animations. Some of the best editing I have seen and the cadence of the presentation matches so well with it and delivers the information at a very natural pace.
I especially appreciate the little caveats that you give. They really help to keep people on track.
exactly this. posted my comment before reading..
I'm a theoretical chemistry PhD, who uses quantum mechanics to study molecules and how they behave.
This is easily the single best explanation I've come across of electromagnetism, light polarisation, scattering, and how molecules interact with light.
I can't wait to see you tackle frequency dependent polarisability in the next one!!
oh, theoretical chemistry PhD, nice! I'm in ...maybe the same field maybe an adjacent one, not sure how it counts.
If you don't mind, I actually had a question about something that's missing from my understanding of electronic structure theory:
do you know how (/in which levels of theory) $E_{\text{rad}}$ (the thing at 5:00) is taken into account in the electron-electron repulsion? The equations I have in mind always use something based on $\frac{1}{r_{ij}}$ for that.
@@niacdoial The joy of being a theoretical chemist is that I don't have to try to be a physicist :p
I probably learned that at some point, but nowadays I'm more focused on solvation through PCM, which is why I was so excited to see this video in particular.
@@AdreaSnow oh gotcha! well, thanks anyway, and good luck on your PCM work!
Wow. I am blown away 🤯
This is a master class not only in physics of light but also in creating amazing animations that show the core of what´s happening.
As a 3D artist specialized in photorealistic imagery. This series pushed me a whole lot deeper into the rabbit hole. I know about the principles of light. But the detail in which you show it and make it understandable for mere mortals like me is mind-blowing.
Handy down one of the videos I resonated the most lately (pun intended) ✨
Will there be soon tutorial how to shade physically correct rainbow-colored sugar water tube in Octane ? :D That would need some explaining what is the point on that, or at least links to these videos.
In reality, it would be quite hard, if not impossible. As far as I know, Octane doesn't have any way to handle polarized light, not to even mention circular polarized light.
We all just got linearly polarized in order to get to this video
Animations are just amazing 😍😍,,, Every professor explaining Maxwell's equations and how it predicts the origin of light, needs this kind of animations to illustrate how certain vector algebra operations is resulting in certain results to visualise what is going on. Really amazing 👏🏻👏🏻👏🏻, In history you will be remembered as one of the youtubers who revolutionaised the process of learning and understanding anything intuitively.
Hard to describe how good this video is other than to say: Nothing has made these concepts more intuitive and easy to understand than this video.
Truly a symphony in animation. Every time I watch this video catch another nuance of EM wave propagation. Deserves a Nobel prize for illustration!.
Wow, an unlisted 3b1b episode! Nice!
Blue doing a double upload in 26 mins is a surprise to be sure, but a welcome one
I have been working with light scattering techniques and have gathered an understanding of the underlying phenomena over many years. This is the first time that i see such a high density of high quality and intuitively understandable visualizations on this otherwise difficult to grasp topic. Truly useful for beginners and advanced alike. Great video!
As an Artist an Math/Science Lover (I`ve watched all af your videos), This touches me deeply, I can only be grateful through a youtube comment, but really and truly, your work has influenced me deeply for years, at some part of the video I clapped out of joy!
Yours truly.
- Juan (Amenaza) Amenabar
As someone who wears polarized sunglasses all the time due to light sensitivity, I have to think about polarization more than people who do not. For instance, I can't view my phone screen in landscape, as the light is polarized from the phone screen, and it gets completely blocked when I rotate my phone to the landscape orientation. I also see rainbow scattering/interference patterns whenever looking at two thin plastic films that are sufficiently close to each other with light passing through them.
LCD screens depend on polarized light such as watches for example. They are polarized in a certain direction for a reason: to make them still visible for people who wear polarized glasses. Of course the polarization direction in sunglasses has to be fixed and consistent in a certain direction because the point of them is to eliminate glare from horizontal surfaces like water.
Also it’s fun to observe car windshields and side windows to see the stress patterns. I don’t pretend to know all about automotive glass but it’s a very complicated lamination process to strengthen it or to have it shatter in certain size and direction of slivers for safety.
Fun fact about phone screens if you use some screen protectors they change the orientation of polarized light, I found this out when I installed a new one on my phone and trying to use gps on the car..
Not all OLED phones have a polarizing filter. I'm actually not quite sure why most do now. I suspect it has something to do with needing to polarize the light it shines for biometrics.
It may be worth doing some research to find a phone without one. Looking into it myself, it looks like the reason they still do use polarizing filters is primarily to reduce glare for easier daytime visibility, but I had a Samsung Galaxy S7 that didn't, and it was really nice to use with polarized sunglasses on.
Also parts of the sky are polarized.
Super Excited for the third part 😁
Amazing how a maths channel gives some of the best science information.
Ooooooh! The fact that part 2 came out just an hour later has made me unreasonably happy! Grant, are you trying to be the best YouTuber of all time? Because this is how you become the best YouTuber of all time.
This might already be one of the most clarifying video series so far I've watched on electric fields (and fields in general). I feel like I've got such an incredible boost in intuition.
Some of the footages of the vector fields might benefit of releasing as stereoscopic 3D? While our brains are quite well trained on it by now, we're still seeing a 3d representation of a field effect, reprojected on a 2D screen. Especially in case of the circular vector motions it became hard to parse how the arrows where exactly moving.
this is a really good idea, i hope your comment gets seen!
Yeah, he did a fantastic job! It's something I've tried many times to explain to people, and it's very difficult to do in words or still drawings.
Light is such a basic yet complicated concept. Look forward to your explanations!
Once again, the animations here are just divine
Challenge Question:
Looking from the light source, the light is twisted clockwise, as that is the direction required to produce the spiral pattern with the "ribbon view" analogy.
We can deduce from that that the light that is rotating counter clockwise is slowed down more by the sugar molecule than the light that is rotating clockwise.
Maybe I just skipped it, or it wasn't in the video, but I do not know it that is left handed or right handed now. It changes, depending if you look at the light from the light bulb or from the screen.
I'm glad someone else posted their thoughts on the challenge question! I got the same result and was hoping to be able to confirm it, lol.
Based on the animation at 18:10, I believe that Grant describes light that rotates counter-clockwise as right-handed.
As for the 2nd question, I think the light with the higher frequency encounters more sucrose molecules on average, and assuming that their proportion doesn't change much at this scale, the rotation speed should be proportional to the frequency.
@@ThePondermatic No, the light is moving to the direction of the thumb, and the way the other fingers curl is the rotation. So right-handed is clockwise when you look to the direction the light is moving.
Here is my attempt at an answer:
As seen in 18:42, right-handed light rotates clockwise looking from the light source to the receiver, and vice versa.
Looking at the video, my intuition says the light is being twisted clockwise looking from the source to the receiver, so there is more right-handed movement.
Therefore, I believe the sugar water molecules are slowing down the left-handed light more; that is, the sugar water has a higher index of refraction for left-handed light than right-handed light.
Something that confuses me however is that at 20:04, after using red and yellow to represent right- and left-handed light respectively, he shows the result of slowing down right-handed light giving a result of a yellow wave rotating clockwise looking from the source to the receiver, which to me seems backwards. Should it not be a yellow wave rotating counter-clockwise from the source to the receiver? I.e, moving to the left? I'm not sure if he's accidentally flipped the direction there or if I'm fundamentally misunderstanding something, I'd love to know
I love how elegantly you are able to explain these concepts that are so hard to visualize without the fantastic animations you produce
Those animations are like straight-to-brain teaching, beautiful work, thank you!
Sanderson’s straight-to-brain teaching method ™️
Thanks for not making us wait for the follow-up videos!
Bro, I can't believe that we are witnessing this wonderful videos for free.
This really blows my mind.
This..... THIS!!!! I've be trying so so long to deduce what a more accurate 3-d representation of how light or wave energies propogate through a medium or field. It's so hard to hold all the variables in your head not even as just a snapshot, but a continuous motion. This is helping so so much. I'm obsessed with wave functions now thanks a lot.
Me (philosophising this evening (India) ) : I don't think I understand light properly.
Grant: I got ya!
I really get goose bumps while watching this video… The abstract principles are perfectly explained by those simple animations. Thank you for your effort for making such fantastic videos!
this is the most comprehensive explanation of how light works i've ever seen. i've never been satisfied with the idea that there were billions of little "beams" of light bouncing off of everything, it never felt intuitive. i feel like i finally "get" it in a way i never did before.
Finally someone explained polarization clearly. Good work!
Grant! You win! Specifically relating to the portion on the propagation of light and electric fields, this is the single, most succinctly informative video I may have ever seen on any subject. I am in awe of your ability to explain complex mathematical topics, and how you employ your animations to do it. None of these topics are new to me, and yet you managed to increase my understanding of them by an incredible margin. I feel as though you have just pulled a veil off the universe and let me see it clearly for the first time. There should be an award for videos like this.
Grant, this is simply brilliant. Imagining how the electric field from a charge (a moving charge) acts on another charge is damn near impossible. The mind of a cave man did not evolve to deal with the task. Yet you have shown you are capable. That is mind blowing.
Do you intent to make an animation showing how the magnetic field oscillates as light is propagated?
Thank you for enlightening we mere mortals with such a brilliant and clear explanation.
this is extremely high quality educational content.
Somebody give this man a medal
the fact that linear motion can be described with two circular motion is fantastic....
PI hides every where
Grant, your videos are the healthiest, choicest tidbits of brain food out there 😩 Every time you upload, it's like eating a full meal after weeks of small scraps here and there. You are a master of the educational craft, and it has been amazing seeing you grow to be the king of YouTube's mathematical content from your beginnings back when I was an undergrad ❤
@oreopoj - 2023-09-01
In all honesty, from someone who completed a 4 year undergrad degree in physics and subsequently went on to do a PhD on a topic that involved polarized light - this video does a fantastic job of explaining the phenomenon and clarified many difficult concepts that usually get lost in the mathematical details about light-matter interactions. Bravo I say! I think it’s the animations that this channel author produces which have a magical way of making traditional static textbook diagrams come to life.
@1495978707 - 2023-09-02
Indeed, we often only ever see the math, and never get intuition for what’s actually going on when it comes to EM waves
@berryesseen - 2023-09-02
They should add a QR code in textbooks that would link to animations like these to better explain the polarization of light. 2D images do not do the job very well, at least if your 3D imagination skills are not the best.
I have an EE undergrad and PhD. EM waves are not my expertise. Until seeing this video, I don’t think that I had understood what they are.
@oreopoj - 2023-09-02
Yeah, that was my feeling too. Did I really understand electrodynamics? The bit about adding a time component to Coulomb’s Law nailed it for me.
@renemunkthalund3581 - 2023-09-03
So true. Excellent channels like 3blue1brown are instrumental in giving students a more 'tactile' intuition of physics and maths.
@aurelia8028 - 2023-09-03
I don't think you can truly appreciate what's going on here unless you've completed an intro course in electrodynamics. There's too much going on here for the average person to actually understand.