Steve Mould - 2020-07-16
The first 100 people to go to https://blinkist.com/stevemould will get unlimited access for 1 week to try it out. You'll also get 25% off if you want full membership. A solution of sugar water can actually change the orientation of polarised light. Glucose/dextrose always twists light to the right! It's all to do with the superposition for quantum states and the chirality or handedness of sugar molecules. Here's my video on why molecules created by biological processes only ever have one or the other handedness (Homochirality): https://youtu.be/SKhcan8pk2w This online wave generator is amazing - https://emanim.szialab.org/index.html (thanks @kehrnal for pointing it out). - Set the two waves to left and right circular, tick the box to show the addition, tick the box to add a material then change the refractive index of the material! Here's a link where that's already set up for you: https://emanim.szialab.org/index.html?7VWwGgABgA Here's Vihart's video on Metachirality which is relevant! https://www.youtube.com/watch?v=8NmHZEKkkpM Credits: First electromagnetic wave animation by And1mu (https://commons.wikimedia.org/wiki/File:EM-Wave.gif) Superposition animations by Pete McPartlan You can buy my books here: https://stevemould.com/books You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Joseph Galliera Nathan Williams Matthew Cocke Glenn Watson Mark Brouwer Joseph Rocca Joël van der Loo Doug Peterson Yuh Saito Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk
I am a chemist. I learned about optical rotation in school and I test optical rotation on a fairly regular basis. This is by far the best explanation I have ever heard and I understand it better now than I did 20 minutes ago. Thank you.
I have a physics degree and this is literally the best answer I've ever gotten to this question. My professors at university always resorted to a lot of math to explain this, but your explanation is so simple, yet so complete.
Your professors wanted to ensure that you wouldn't get a physical understanding. They wanted you to have only a mathematical understanding. In general, they want you to have no physical understanding.
if you had a solution of levose (dextrose stereo-isomer) it would , of course polarize light in the opposite direction. If you mix dextrose and levose together, you could determine the ratio of each substance by how much and in what direction the light is polarized.
Or he could have added an equal amount of L-Glucose and had no rotation of light. He seems to ignore that D-Glucose has a levorotatory form in L-Glucose.
l-Glucose was once proposed as a low-calorie sweetener and it is suitable for patients with diabetes mellitus, but it was never marketed due to excessive manufacturing costs.
The acetate derivative of l-glucose, l-glucose pentaacetate, was found to stimulate insulin release, and might therefore be of therapeutic value for type 2 diabetes.[3] l-Glucose was also found to be a laxative, and has been proposed as a colon-cleansing agent which would not produce the disruption of fluid and electrolyte levels associated with the significant liquid quantities of bad-tasting osmotic laxatives conventionally used in preparation for colonoscopy.
I thought, honestly that was a fatal mistake to eat much of that.
I found this explanation to be fascinating but kept waiting for the corroborating demonstration of the L-glucose case which sadly never came. But wait. Wasn’t he using sucrose there?
That is what you call a racemic mixture
I worked for a decade and a half in sugar mills as a "Sugar Chemist"/Lab Technician. We did indeed us polarimetry to determine the amount of 'sugar' in the crushed cane juice at the start of the milling process and the processed raw sugar at the end. We also had a process to determine levels of fructose and other "reducing sugars" by measuring the angle of light bent to the left (levo-rotary).
0:00 - Introduction
0:44 - Polarized Light: short explanation
2:31 - Polarization of Sugar
3:49 - Superposition of Polarized States
3:55 - Superposition of in-phase waves (linearly polarized light)
5:17 - Superposition of 0.25λ out-of-phase waves (circularly polarized light)
6:33 - Superposition of circularly polarized states (linearly polarized light 😮)
8:01 - Pasta
9:53 - Index of refraction of pasta
10:52 - Superposition of pasta shifted states (wave-plate retarder)
11:20 - And to Reiterate...
12:17 - PASTA SYMMETRY
13:40 - Handedness (fundamental common attribute between pasta & sugar molecules)
14:36 - Mirror symmetry in molecules
16:12 - Answer: "Why Sugar Always Twists Light To The Right"
16:25 - BTW: Dextrose
Thanks!
Hey Steve! You could extend this to explaining how liquid crystal displays work really easily! Basically just using a voltage to orient chiral molecules either along the direction of the light, or perpendicular to it, which then either make it through the polarizer (bright pixel) or don't (dark pixel). Thanks for some great animation, this will definitely help me teach polarization a bit better!
Don't need a video for that you just explained it perfectly here. wow.
“Watch what happens if I turn this pasta upside down” - Steve Mould, 2020.
"It's genuinely unremarkable."
It was genius. He's making it seem really simple, but I'm sure I'm not the only one who made the reasoning mistake he explained in the beginning.
We need a Steve Mould but out of context
Watch what happens if I turn this pastor upside down.
He made a video about that already
Thank you, Steve Mould, for bringing to light (pun intended is in a superimposed state with pun not intended) this very thorough and comprehensive explanation of circular polarisation. I've always heard the term being thrown around, but the actual physical meaning of circular polarisation had always eluded me before now.
I’ve been trying to understand this for years, and this is the first time anybody actually explained it to me. I think part of the secret to his success is that he is genuinely curious and is answering questions that he had himself. It helps put him in the audience’s shoes. Taking your audience through your journey of you came to understand something yourself is very effective.
7:20 At the time when both helix waves are at the same position, their superposition should actually be twice as far from the axis, since adding their position vectors would give you a location two times further from the axis. The general wave form will still be a sinusoid, just the amplitude should be two times bigger.
I've seen this video of yours multiple times. Each time, it makes sense, and yet I'm pretty much 100% certain that I wouldn't be able to recount it properly.. Fascinating, intuitive, and basically un-paraphrasable 🙂 Keep it up!
Thanks Steve for making this very complicated phenomenon understandable (Well, very nearly. I got lost right at the end. I feel a rewatch coming).
I think this is one of the most important videos about light on Youtube and it's definitely going in my favourites folder.
Photon A: how was your day?
Photon B: Terrible, I kept bumping into flaps of pasta.
Photon C: What the hell is a "day"?
Technicaly they are not photons they are oscilations in the magnetic and electric field. Together they make a photon(superposition of those 2)
@Frano Lucic Technically, it's spelled technically.
Also, the comment you replied to was technically a joke.
@I'm Very Angry It's Not Butter Proton D: Ahh! Talking protons!
Wave-particle: what are these old timers still doing here
Wow that's exactly how polarimeters work! Ever since I learnt in high school that optically active isomers rotated polarised light, I always wondered how exactly.Now with this superposition of superpositions concept I can finally see how!Thanks Steve for providing such high quality content!You are truly awesome! 👍
I just came back to this one for a re-watch. This is truly excellent coverage of the material. You are master of your craft, Steve.
Thanks for making this. I teach polarimetry and will point students here. I had a hard time explaining the random orientation being a no issue at first (maybe because im very visual so I had no problem working thorough the orientations in my head ... I was just confused why anyone would think that). So thanks for givibg me tools to better communicate all this. You did a great job!
I used to love organic chemistry but never really got a satisfaction kinda thing from studying and pretty much forgot about it. Looking at the start of the video, it instantly reminded me of all the stereoisomers, racemic mixture, chiral carbon, etc stuff that I had studied, and it actually makes things more interesting. In reality, this concept is so difficult when studied with all the technical jargon that students face difficulty to garb on to the concepts, but the way you explained it makes it so easy to relate and a lot of things that I don't know how to put into words here. XD
Super amazing video.
Really great stuff! I have been taught before that chiral (handed) molecules rotate circularly polarized light in a characteristic way, and have done circular dichroism experiments in a lab before, but it was mostly covered as a fundamental attribute of anything chiral. This is a great visualization of why that property arises from the chirality.
Also, as a biochemist I’d like to mention that the reason that sugar as we know it is virtually all one-handed and not the other is that the enzymes that make sugars are ALSO chiral and make “left-handed” molecules preferentially over “right-handed.” Which is true of virtually all biological molecules, at least to my knowledge, which is absolutely bonkers!! The building blocks of our bodies and of, like, all living things preferentially have a certain chirality 🤯
Actually, all natural sugars are right-handed.
I'm a chem major in college. He just gave an organic chemistry lecture to lay people and it made sense. Steve Mould is amazing
Edit: a year later and I'm almost done! My last final is in 6 hours then I'll have completed my bachelors! :D
No. He just gave a physics lecture that chemistry students could understand. That's even more impressive :)
@khaitomretro ...shots fired
look at this flextrosexual
He lost me halfway through, then blew my mind when he put it together.
@khaitomretro this is the principles of optical quantum computing I think
Very cool intuitive explanation. Don’t know how I missed this video when it came out
Wonderfully made, thank you!
Also, sucrose turns polarized light +65 degrees. If you split a sucrose solution into one of glucose (+52 degrees) and fructose (-92 degrees), we have a net change of optical rotation to -40 degrees. The direction has been inverted, and hence it's called inverted sugar syrup.
Why can we assume that all molecules are oriented either upwards or downwards? Surely the light hits molecules in all kinds of orientations at all kinds of angles. But if some light was always blocked the solution shouldn't be as transparent 🤔
@Koloblicin Basically, the molecule slows down the light that travels through it, but doesn't absorb it (screws and pasta are opaque but a molecule of glucose is transparent). When a molecule is oriented perpendicularly or something, it just slows down both components equally, so has no effect on polarization. Under an other angle, it might have a reduced effect: for example the clockwise portion crosses the "helix" 21 times while the counterclockwise crosses it 19 times, and therefore travels a tiny bit faster.
the animations were GOD SENT aaa they were so helpful to understand <3
dude
im always impressed by how knowlegeable you are
and by how smart you are in explaining
you REALLY understand the thing
others speak well but have limitation themselves..
THANK YOU A LOT
♥
I love your explanations! You put them in a very real world way and their importance for how they make many technologies we take for granted... work. You’re videos are amazing and I can’t begin to express my appreciation! Keep doing what you do, and I look forward to all of your videos! Thank you for adding knowledge to us all from an extremely knowledgeable person!
Grammatical error meant your and when I meant extremely knowledgeable person I mean you are an extremely knowledgeable person! I’m just an avid learner lol and I can’t wait to keep learning from all of your videos!
This explanation was leagues above any explanation I learnt at school about optical rotation. Thinking of linearly polarized lights in terms of two circularly polarized components was basically what I needed to get this concept through to my brain. That was amazing!
I agree, first time it clicked. visual learner here
I mean it kinda makes sense since there are similar concepts in maths as well
Was your stash in shot?
Yep, several pennies finally dropped for me too!
Which school did you go I didn't even knew about this up till now.
This explains everything! Polarization is now explained! I was long confused by the "insertion of 45* polarization pane between 0* and 90* causing light to partially pass"
The best explanation ever! Thank you! I am a teacher and I have a master's degree in physics and this is so precious! If only we had such explanations 10-15 years ago to make it easier to understand!
Explained much better than my university Physics lecturer did over a 3 week period. Fantastic work!
Amazing! I think this explains something I've always wondered about using a 'circular polarising filter' on a camera lens - turning the filter alters the brightness of light from the sky/water etc. I never could understand why turning something 'circular' could have that effect - now I know!
Thank you for bringing it down to a level that more of us can understand ;-)
This video for me is up there among your best ones, Steve. Never learned about polarization with such clarity. Kudos man.
"I've chosen a wavelength of light that matches the spacing of the pasta spirals" - a sentence not spoken often
The Italian chef scientist
A brand new sentence in the universe
Looks like something in the sub-radar range https://i2.wp.com/yatebts.com/wp-content/uploads/2018/11/Frequency.png
@Greg Bernstein Lol!
@Greg Bernstein Thank you! I was about to look it up :-D
the way youve explained these topics in such a fluid manner is amazing. loved it, would surely help my understanding get better in school :D especially the diagram and the animation that was shown, so so important in understanding superposition
Steve, I must say honestly I find your channel to be the most interesting content on the web. No joke. Kudos.
The best explanation I've ever seen of optical rotation with chiral molecules.
Also, the best explanation of circularly-polarized light.
This video is real progress in science education.
Hey, I actually just read about this circular-to-linear polarization superposition while studying for my MRI thesis.
I didn't quite get what it meant (and it wasn't hugely important in my case) until now! Thanks, Steve!
Oh my God .!!!! I have been searching this kinda video for 3 days to clear my concepts about how glucose and fructose rotates polarized light ...and yes!!!! I found this video ...thank u soooooooo much !!!!! The experiment is so satisfying .!!!❤
Alternative title for this video: how to finally understand why in God's name optical isomers are different, how are they different and what the hell does "they bend the light right or leftwards" mean. It's amazing how you get a topic as hellishly complicated as optical polarization applied to chemistry and make it sound like it makes sense.
Also, I think a good follow up for this would be why the direction the molecules twists the light matter. The case for thalidomide is famous: when it twists the right to the right it's a sedative but when it twists to the left it causes birth defects. How so?
Because right-handed molecules don't fit on left-handed "slots", and as far as nature is concerned, they are completely different molecules
The above explanation is correct, differently oriented molecules fit into different molecular receptors in the body. Hence the weird 'double personality' of otherwise identical molecules.
A large part of the reason is that many/most molecules in biology, are chiral. And therefore can react differently to the different enantiomers of a molecule.
@FranchuFranchu I vaguely remember reading somewhere that certain molecules when encountered in the human body (perhaps 'biologically' would be better) have a consistent handedness, but those created in the lab (perhaps 'chemically' would be better) do not, and at the time the author wrote that, the cause was unknown.
Have we figured this out yet? have we figured out how to 'artificially' recreate the handedness of molecules yet?
@temseti0 They usually create both and filter out the undesired ones
This was amazing. I've been trying to understand polarized light all day, and you finally made it make sense. Thank you.
I love your videos Steve and wanted to thank you for them! I have been researching patterns across disciplines (my primary discipline being music) and it has been fun to discover and notice more connections with the help of your videos. You rock!
You’re insanely amazing at explaining things
Beautiful. This is the peak. Nothing can top this explanation for this concept. Just beautiful. I think I'm gonna cry.
Oh wow. This is amazing! Thank you for the explaination. I haven't even known about this weird behaviour of sugar. I'd love to show it and try to explain it to my friends and family.
I eventually just accepted that chiral molecules twist linearly polarised light and never questioned why exactly that is. In all the chemistry and physics lectures (even in optics where we talked about many polarisation effects, so it would have been perfect to give an in-depth explanation of this phenomenon) we were never explained why that is. I'm so amazed of how comprehensible your explanation was. Thank you so much for blowing my mind.
Profs usually can't explain it in a comprehensive way because they don't fully understand it themselves.
I always had this lack of clarity when it came to chirality. Well, now it's sloved.
@Marv1451996 Not always the case. Good institutions usually have excellent professors. What matters is whether the students are curious or not.
It was explained to use during the first semester for the first time and repeated/applied several times so far...
I'm studying bioinformatics.
It's weird how much of traditional teaching (or maybe just how some school curriculums were set up) was just learn the facts / models instead of explaining why, visualizing it, or even just explaining why it's useful. Now that I'm older I"m more willing to take up dry reading like wikipedia while also checking out youtube videos for that extra insight, and when I find them I"m stupefied why this wasn't in school because it seems like such a small investment in extra explanation for the huge help in understanding. So I've learned enough that way so that once he said helical polarization is possible, I immediately figured out a helix is chiral, the sugar molecules must be, there we go. Still kept the video playing for the watch time lol
I've been searching for ages for an explanation on both the web and youtube, this video is the only one that explained it to me, I was felt that it's counter intuitive because molecules are usually not all oriented the same in a solution.
Amazing work Steve, this is the best one of your videos I have seen so far! 👍
I have tried to understand what is circular polarised light is from wiki and it is totally incomprehensible to me. The phase shift of electric and magnetic components are most clear and simple explanation with your visualisation. It just makes me understand immediately what it is about! Thx a lot.
Thank you for finally explaining this cool effect to me, wondering 2 decades ago in school already 😁💪
this is the most convincing way of explaining chirality and the reason why molecules turn light the way that they do. Hands Down. Amazing.
I wonder if you can twists the polarization of microwaves with cooked pasta.
You, sir, are a genius!
Oh my god that's brilliant. The wavelength is a match, so... probably?
FBI wants to know your location
@Simon Vetter haha no you need The polarization to be oriented vertically/horizontally and the microwave doesn't have a polarization filter so overall net-value is zero, the comment above was purely for the sake of good humor
A microwave oven works by passing microwave radiation, usually at a frequency of 2450 MHz (a wavelength of 12.24 cm)
That's probably to big a wavelength for the pasta to have a strong effect 😞
Thank you for the explanation and the 3D animations were suberb! The visuals made it so much easier to imagine the whole thing
@neilrhythmcode - 2020-07-16
I just tried this and it turned the light both ways!
Turns out my solution was Ambidextrose.
@insanimal2 - 2020-07-19
hah!
@chadwickposey7806 - 2020-07-22
Angry upvote
@zero-twentysix - 2020-07-22
This is good. This is really good. Have a like.
@jamesr1894 - 2020-07-24
/facepalm
@deano43 - 2020-07-25
My one didn’t do anything, it’s dyslexic !