the faraday effect
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- Опубліковано 21 вер 2024
- So much failure in this video---but that's how we learn things.
Polarisation en France (article about Light, Napoleon and Egypt): onlinelibrary.... did not really like this article though.
Circularly Polarized to Linearly Polarized gifs:hackert.cm.utex....
Sir Lawrence Bragg: • Electromagnetic Waves ...
the most important material in science: • the most important mat...
Pronounce a Dutch name: • Dutch lesson #4: The o...
Faradays Diary: archive.org/de...
Florencefst- old timey experiment: • Faraday effect
Support me on Patreon and I will buy more optics equipment: / acollierastro
33 years old french scientist here. Just enjoying my last years of this earth with those great videos.
Before antobiotics came around in the 1910s; the British had a way of dealing with infections perhaps Joseph Lister's Antisepsis System among others and believe that the french lagged behind in dealing with infections until antibiotics come around. The British and likely parts of America had ways of dealing with infections prior to antibiotics. Just a guess.
Pretty sure that the mortality data has been skewed by French post modern philosophy. It's not good for people and the depressing malaise can't be physically tolerated for more than 40 years or so. If they could stop reading the likes of Foucault or Camus for 10 or 20 years they would find that their health returned. Liberty, Equality, Fraternity!
☹ Damn, I'm so sorry (about the french part)
As long as you are not messing around with optics, you should be fine.
"insert hidde the pain harold image"
"I'm so afraid of magnets." That's smart. Magnets move on their own and feel no remorse. I'm terrified of the big ole magnets I work with.
are you saying that poltergeists and magnets are the same thing?
They're not not saying that.
Yeah those strong rare-earth magnets are really a thing that seemingly can have you have one less finger. When people use them to pin things to a board, I think they really should coat each magnet in some foam material to not get their fingers’ skin damaged with a click, and also to make magnets live longer (in case they click too hard or fall to the floor).
@@05degrees
I imagine it's hard to manufacture a foam that can withstand forces that can break bones being applied to it with every use.
The clicking is a feature of magnets that you can't really engineer out without just making a weaker magnet, so whatever protective coating or surface will have to withstand those intense forces all the time without becoming damaged or worn through.
It's sort of like trying to engineer an accident-proof bullet. If it's safe enough that you can't hurt yourself, it's also weak enough that it doesn't do what it was made to do.
Why TF does magnets have a right hand rule but not left ? Maybe Angela knows.
Galios, one of the biggest deal Mathematicians of all time:
1) was french
2) died at 19
As a result of a duel though not because of a sudden disease. That being said your point is taken.
Galois*
I remember this from _Numb3rs_ when the math professor's advisor was telling him, "Don't get involved in politics, Charlie. That's how Galois got killed."
The amazing part of that story is he knew he would die in the duel so spent the night before writing down all the things he had been thinking about. His friends took something like 6 months after he had died to understand and publish what he had written, but that became “Galois Theory”
@@seanhunter111 I'm quite glad that as a society, we've mostly realized that honor is WAAAAYYYYY overrated and not worth dying for
Angela flexing on us with a $700-$800 Faraday Rotator she just casually keeps in her house while also saying "I'm not an experimentalist."
Love it.
@@tolep”publishing”?
@@tolepcan I have your mother’s email please? I need to inform her that her child was not worth publishing
@@tolepi mean yeah this is basically the kind of demonstration you'd show if you were a TA to a 1st year undergrad class, it's not meant to be cutting edge research
@@tolepcongrats sir you win the yike of the day
Rumor has it she keeps a particle accelerator in that frog box.
If John Green has taught me anything, it's that everything is tuberculosis
I thought he had cancer though? Too soon? Ah screw ya’ll I think I’m funny
wrong brother @@Hacob_R
@@Hacob_R it was kinda funny! he might even laugh lo,l he seems to have a pretty good attitude about the whole ordeal all things considered!
@@Hacob_Rwrong brother:p
@@Hacob_Rthat was Hank that had cancer.
Angela: "Don't judge my books."
Me: "Of course Angela owns Maus and Persepolis, because they're awesome and she's awesome."
You know, there is a reason why they are there. It's because......
The faraday effect in the atmosphere is actually extremely critical to long-range (non-line-of-sight) radio propagation. Not only does it randomly polarize shortwave-and-lower radio waves so that horizontal antennas can communicate with vertical antennas, the rotation plays a key role in those radio waves bouncing off the ionosphere instead of going straight through into space.
Without it, over-the-horizon radio communication would be nearly impossible. There's some minor effects you can use to get some frequencies of RF to 'hug' the earth a bit to reach a short distance around the Earth, but when the sunspot cycle is at a peak, a lot of frequencies will propagate around the earth multiple times.
Obviously, it was Skynet that send back terminators in time to make sure French physicists would die neither too early nor too late in order to bring about its existence. One bad sequel after another. And some getting in each other's way.
On a more serious note, doing the quantum computations to get the same constant we have already measured is actually good work. It's something that should be doable and it just proves the validity of quantum mechanics a bit more.
I find it astounding that people back then even considered the idea that light and electromagnetism were connected, given that in our everyday experience, light couldn't seem to care less about magnets.
This was also during the romantic era so the idea that everything was somehow connected and part of one whole was in vogue. Even though scientists weren't writers or poets they were still influenced by the dominant cultural waves of their time and we can see this kind of thinking pretty explicitly with Ørsted who discovered the connection between electricity and magnetism. In his writings he was pretty explicit about his romantic influences, which isn't surprising given that he lived in Denmark which was one of the countries that had the strongest romantic cultures.
Science and culture tends to have a pretty interesting interplay like that, On The Origin of species is often credited with kicking off modernism by introducing the idea that history has grand narratives. Quantum mechanics would later go onto influence expressionism and nihilsm. So even though scientists might not themselves directly interact with art they often are indirectly influenced by it and themselves influence it, sometimes very directly.
@@hedgehog3180 I think another takeaway is, science rewards checking and finding out!
If it moves, it's biology. If it smells, it's chemistry. If it doesn't work, it's physics.
You're right, physics doesn't work because energy does work
if it doesnt do anything, its math
@@er4795 Heeeeey!! 😑
…well technically you’re correct, math is its own thing. But that’s too formalistic!
Ahahahaha; you think biology works... We had a saying in the lab I did my Masters in: "If it works 60% of the time, it's a miracle; if it works more than that, you're doing something wrong".
haha, a magnet moves but I ate one, I love smells and I'm a chemist, but I get work all the time in physics. I just wish I could get my electronics to work so that I could make my math work out. Gr8! Peace ☮💜
Faraday invented a precursor of the Bunsen Burner, so I think he used something very similar to a proper Bunsen Burner, of Faraday's own invention. Because he's just that cool.
I didn't know Faraday did that! I do know that the tube with burning gas shown in the video is not a Bunsen burner.
@@HelgeMoulding Actually, he invented the Faraday Burner, which didn’t catch on because it wasn’t alliterative.
It’s all in the marketing.
Before the use of electricity the cutting edge technology WAS light production. Because everyone wanted good light and when the sun went down no one had it. There were options fish/whale oil, gas, or even a roaring fireplace.
@@deepdrag8131He should have gone with something like "Fara-daylight" or "Fire-a-daylight" or simply "Fire-a-day" with a tagline 'Your night fire that shines like daylight'. Yeah, but he was too busy working on the less important optics. He could have been big, but he was simply not smart enough.
It's not like he had to do the optic experiment at night he probably just used a window or the sun as a light source directly. Why would you bother with fuel fire and all it's dangers and costs when you can point you're setup towards the sun and have a free light source? It should be relatively easy and cheap to channel the light from a window with even the most basic of setups?
Michael Faraday spent five years making optical glass, and if he hadn't quit that to experiment with electricity he would have probably died of heavy metal poisoning like everyone else who was experimenting with glass ingredients at the time. Although, he did have a nervous breakdown a few years after he quit experimenting with the heavy metals.
He was almost killed making explosives for Humphrey Davy too.
And, like Spinoza a couple hundred years earlier, anyone cutting lenses and breathing in the dust would've been much more susceptible to major harm from respiratory illnesses.
"I'm so scared of magnets." - A.C.
Me looking at my healing bruise from two neodymium magnets being put too close together, with my hand in between: "I can relate."
We use Fresnel constantly in game dev - it’s incredibly useful for faking things like rim lighting, ghost effects, or masking the fresnel angle of an object to create some effect that avoids the boundary angle from the camera. Love that guy. Games would not look the same without him.
..except that a fresnel shader doesn't do anything described by fresnels equations. It just increases material reflection based on the product of camera angle to surface normal. IRL material properties don't change based on where you are standing. Fresnel shaders are complete hacks. So we don't actually use fresnel at all, we just call it that because it sort of looks similar.
When they were doing the old-timey experiment, all I could think was my optometrist's voice asking, "Is it polarized through one....or two?"
One?... or two?...
Underrated
@@theblackherald
the old school eye testing thing that was on an articulated arm , had many lenses and filters, and the optometrist would do a binary search through tens of thousands of possible lense combinations by flipping back and forth between "one or two?" about a dozen times till he honed in on the best prescription for you.
Now they just have some autofocus camera looking at your retina that spits out a number.
@@petevenuti7355 They definitely still ask this after they do the camera. I just had an eye four weeks ago.
@@sp0ck1p "I just had an eye 4 weeks ago" ... Ahhh, you don't have any eyes anymore? Or did autocorrect just wholesale remove the word exam?
10/10 no notes on your character analysis of Napoleon in Egypt.
Napoleon was a pinch more panache than Bush
I'm a ecologist, so all the quantum quantum quantum goes over my head, but I appreciated the visual demonstration of all the ways a faraday experiment can go wrong
Having taken a minor in physics (while studying math) lo these many years ago, and having had to re-create the Cavendish Experiment, I have the utmost respect for experimental physicists. The attention to detail required to get accurate measurements is terrifying.
Cavendish is especially impressive because we still aren't doing that much better than him. He got it within 1% (10,000 parts per million), and we're currently at around 22 ppm. Which is 500 times better, but over more than 200 years. A lot of other measurements of important values improve at (extremely approximate rule of thumb:) an order of magnitude per decade until we sort of run out of steam. So you'd expect 20, maybe 10 or at least 5 orders of magnitude over that time, instead of like 2.7
There's a famous unsolved mystery in history where the French population growth mysteriously slowed in the 1800s and historians don't know why. Not saying that's related to your mystery about French physicists coincidentally dying young, but I think it's interesting.
Those of us who are familiar with John Green's work to combat tuberculosis aren't actually surprised that there were many young people dropping dead "of a worsening cough."
Do you have a more specific time window?
The french Population growth slowed in the early 1800 because two decades of war and hardships killed all the young men
It is not a mystery at all
And of course war increases the rates of epidemy, tuberculosis included.
Hundreds of thousands of yound frenchmen died on the battlefield. Everyone forgot but it was as catastrophically terrible as ww1.
@@Taletad and Paris had very bad water supply for centuries.
World kinda sucked for the living dying and going to war every week… I wouldn’t have babies either.
Its not only physicist its also mathematicians doing algebra which dies in France. Galois and Abel both died in France around that time.
Many many people died of diseases back then - no antibiotics until 1910. Must really have been horrible and frightening.
@@redsky1433 Galois died in duel.
Don't forget Carnot.
@@KycilakAlways saddened me that somebody that brilliant died doing something that dumb.
@@redsky1433antibiotics weren't available until the 1930s - sulpha/sulfa drugs. That's why so many people died in WWI. The regime for treating TB wasn't available until, like, the 1960s
Can't wait until someone comes up with the faranight effect
Faraday Night Fever
omg babe wake up new dr. collier just dropped
they're multiplying
hey that's my line
This only works on Saturday morning
Jesus Christ why do people still do this? It is affecting my mental health. I just don’t understand.
I miss when people would just say 'first!'
Hi Angela, I'm Steve from Adelaide, South Australia. I've been on leave from work and only discovered your channel a week or so ago. Thank you, thank you. I'm not a scientist of any persuasion but wish I was. I've watched as many of your videos as I could and while your knowledge is lightyears beyond mine I've always loved science and it's method. Your humour, knowledge and humble approach is wonderful to watch. Sincerely, Steve.
“and now we have the internet”
It amazes me just how many different fields of study end up here.
it's a real technological marvel, innit
28:08 For what it's worth, Faraday Rotators can used on high power laser systems to prevent damage from back reflections. The big laser facilities are built such that in order to keep the beam power low enough to not destroy the opics, the laser beam is made wider, then it's amplified, then it's made wider, then it's amplified again.... however, if the laser light reflects off whatever you're shooting and goes back down the laser chain, it gets amplified, then made narrower (focussed down), then amplified again... and so on until you've blown up the amplifiers on your multi million pound laser system 🙃
Old timey light source-- starting in late 18th century there were oil lamps with tubular wicks with springs to keep them at the right height and pressurised oil wells, they burned brighter and more consistently than candles.
Scotland was home of Europe's best medical universities in the 19th century... whereas France was rocked by ongoing revolutions/civil wars through the century. 19th century life expectancy in general was probably lower in France vs Britain. fwiw. I don't have stats off the top of my head.
If you remember "floptical" disks (like the LS-120 Superdisk) from the 1990's, those used the Fariday effect to read the bits off the disk. The laser head would measure the polarization angle of the reflected light to determine the orientation of the magnetic field on that spot of the (plastic) disk surface.
I still have some PD-640(toray and Panasonic )and 1/ 2 GB DVD-ram disks.
It used the same technology and as I understand it contains a lot of tellurium, it was also known as "phase change optical" and worked something like a liquid Crystals, but it also used no magnetic heads so I'm not sure if what you're talking about is exactly true, I expect it to be more dielectric field then the magnetic field.
I also didn't know that the read lasers used polarization to do the reading but it makes sense from what little I do know. If I knew that 20to 30 years ago I would have used that knowledge to modify a drive so that the polarization percentage was measured and could make each bit on the disc a value from 1 to 256 , Go two sided with a little higher accuracy and have a half a petabyte on a single disk!
But you know how corporate works , they don't want to give you the best technology they want to sell you everything they can, in small increments, over the course of decades, leading up to the technology they invented 50 years ago. Lifetime of secure income, off each idea.
One cool property of the Faraday effect, which leads to the Faraday Isolator, is that the direction of polarization rotation is independent of the direction the light is travelling through it, unlike a quartz crystal rotator, which rotates the polarization CW from one direction and CCW from the other. So, you arrange your polarizing filters, quartz rotators and Faraday rotator such that, in one direction, the polarization is rotated 45 degrees by the Faraday rotator, and then undo that rotation with the quartz crystal rotator (0 +45 -45 = 0). In the opposite direction, the polarization will be rotated by 45 degrees twice, and will get rejected by the filter, or polarizing beam cube at the input (0 + 45 +45 = 90). The design I'm most familiar with consists of a Polarizing Beam Cube | Faraday Rotator | Quartz Crystal Rotator | Polarizing Beam Cube. P-polarized light passes through the first cube polarizer, is rotated +45 degrees by the Faraday Rotator, -45 degrees by the Quartz Crystal Rotator, and passes through through the second cube. In the opposite direction, P-polarized light passes through the Cube Polarizer, is rotated +45 degrees by the Quartz Rotator, +45 degrees by the Faraday Rotator (making it S-polarized) and it is rejected by the Cube Polarizer on the input side, into a beam dump.
Mantis shrimp are able to use circularly polarized light for communication, which is pretty neat.
I’m currently waiting to hear back about my PhD applications for experimental cosmology programs and watching you do you best with the optical table and then admit “I’m not an experimental physicist” cracked me up so much. Another great video as always!
I'm happy to announce that my girlfriend has been converted to "that sassy science woman" as she puts it and now watches your videos with me
Great video, Angela! Another important reason we use Faraday Rotators to prevent back reflections is that we don't want back propagation within the laser's cavity, because it can cause all sorts of undesired effects on the laser's gain medium.
5 min in and I already have answers to polarization questions I've had for years! Amazing content
“It’s doing the thing!”
If I had a nickel for every time a French physicist who made great strides in the field of optics died tragically young in their 30s from disease, I'd have 2 nickels. Which isn't a lot but it's weird that it happened twice.
My 8-year old son's really into puns right now, and he wants you to know that "a FAR A DAY keeps the crushing experimental failure away."
Ouch
🔥
Came over after hearing about your channel from Professor Dave.
And now I've got a link to old-timer experiments.
The rabbit hole deepens.
And it's awesome.
I also love that you're ready to put yourself out there and show the failed experiment, because learning from failure is something we should expect and learn to appreciate.
Not a historian, but a small glimpse at France:
Firstly, the 19th century is sometimes called the long 19th century in European history. That's because some mayor things happened right before and after and it makes less sense to put down a border in the 00s when the social consequences were still ongoing.
We have the French Revolution in 1787 which lasted until 1799. First this went after gentry and royals, especially 1789, but then the whole thing turned into the Reign of Terror over time and it wasn't fun for anyone.
At the end of this everyone was fighting, specifically the French Revolutionary Wars, which are 2 wars 1792-1797 and 1798-1802.
After that was done, all of Europe had the Napoleonic wars 1803-1815. They are called this because Napoleon was beating up absolutely everyone up instead of French infighting. This included Britain and conquering significant pieces of the whole continent like Germany, Austria, parts of Italy, Spain and Portugal. Then he made the mistake of trying to invade Russia during winter and got beat up on the way back by a multinational coalition. They exiled him twice, once after he escaped the first one. Now idk if scientist got drafted during that time, but they had an absolute outbreak of typhus on the way home and brought that back home.
Now, after the beheading of the French royals, every other monarch in Europe was shook, because if peasants can behead one, they can behead the others too. They agreed that things should be put back as before, more or less. That whole debate was called the Congress of Vienna since they met there for a year. France lost some territory from that.
As you can guess, the nobles weren't really making things easier on the poor. (The British have had mainly the plus of no longer blockading France by sea and fighting in wars, so everyone young with enough money started traveling Europe again. "The Grand Tour" is the reason why you have Mary Shelley hanging out with Byron in Switzerland when she wrote Frankenstein. That and the volcano. Also absolutely a regency thing, especially since you had steam trains getting started, making everything faster and safer.)
Anyway, so the poor weren't really happy to have the pre-revolution bs back when a new king took the crown in 1824, so you had the July Revolution in 1830. (This is the setting for most of Les miserable.) They only crowned a different king this time, so it wasn't as radical, but people sure died.
The July Monarchy heavily favoured people with wealth with the proverbial laissez-faire politics, so there was a failed revolution attempt in 1848. The Revolution of 1848 sparked revolutions all around Europe, since royalty wasn't being great there either. The second republic got overturned in 1851 in a coup de etat by some nephew of Napoleon proclaiming himself Emperor.
This leads to the Second Empire (of France) where they were fighting some "light" wars like the Crimean War 1853-1856. That was mainly against Russia, for who gets access to the Black sea (still relevant today :/). It's probably today best known as the war where Florence Nightingale did groundbreaking nursing work.
This came to an end in 1870-71, with the Franco-German war or War of 1870. Most German states were still pissed France beat them under Napoleon, France was trying to reassert dominance on the continent and also eyeing the slow organisation of German states together with trepidation. That said, Prussia started the war under chancellor Otto Von Bismarck to explicitly kick in the front door Paris and unify Germany. They had been working for that with several other wars against Austria, Denmark and each other for a while. Somehow absolutely pulled it off and crowned the King emperor in Versailles in 1871 and France was mad about that for sure. As always, people at home died which is why there is the dip around that time.
After that you have the Third Republic. Being the losers of the Franco-German war, they had to pay Germany reparations for losing. There was also a financial crash in 1873, so that didn't help.
It also engaged in the "Scramble for Africa" mostly between 1884-1913. More or less colonialism Olympics between France and Britain, the British tried to get a length of colonised land from north through south of Africa, while France was trying the same only from east coast to west coast. So no way these interest didn't collide in there. And one French dude was trying to make the Suez canal happen, which succeeded. Absolute horrible era, but they were terrorising people in the colonies and plundering riches (because they needed the money), so until the start of the first world war it was also the "Belle Epoque". The industrial revolution has also been going on. You get early cinema and photographs, telegraphs, automobiles like peugeut, the Eiffel tower being build, electric lights with paris being one of the first cities being electrified, germ theory and radio activity being discovered. In art you have Picasso, art nouveau, expression, impressionism, japonism, fin de siecle around the turn of the century. Thus ends the long 19th century when the hunger of colonialism finally collides in the first world war.
I hope this made you a bit more interested in the long 19th century, which sure was long. It's no accident you had Victor Hugo and others writing a lot about the plights of the poor. The literary movement realism started in France in the 1840s as a response to the absolute vile conditions for some and pulled no punches. For the first time, paintings actually focused more on ordinary people as well, showing everyday people and workers instead of just royality and people with money. Alternatively there is also naturalism, though they overlap to a degree. Well known works are Middle march, Mark Twain, John Steinbeck, Upton Sinclair's The Jungle, Jack London, Balzac, Alexandre Dumas (three musketeers), Madame Bovary by Gustave Flaubert, Tolstoy, Dostoevsk, Anton Chekhov, Henry Ibsen and you could argue Charles Dickens.
I was hoping someone would summarise the Long Century.
There's also a lot of weird weather due to volcanic activity which affects harvests, the amount of sunlight that people get (which affects Vitamin D production and the immune system). Plenty of strife due to famine and starvation (whether used as a tool pf oppression by governments or due to Nature). Food storage and freshness were issues.
Major volcanic activity always (perhaps falsely, perhaps rightly) is correlated with disease and "plagues".
The mid-to-late C19th big towns and cities were overcrowded slums if you were poor.
There was the outbreak of cholera in London whose source was identified by John Snow that led to improvements in water and sewerage.
Hungarian doctor Semmelweiss worked on cleanliness for hygiene to the medical (surgical) profession.
Lots of dust and soot from factories and homes. It was a coal/wood and steam powered world (even if that was for electricity generation).
Animal waste in the streets (mainly from horses but there would also be animals "driven" to feed on commons and to slaughter).
The chemicals from industry and from fads (arsenic make-up, uranium in glass and plates).
As Angela found a link with optics then the development of photography (Daguerrotypes and photographic plates) and lighting (gas, chemical and electric) may be relevant. Some combination of how diseases transmit in close proximity and how there are all these factors affecting health and the immune system.
(I partly remember a reference to an earlier Krakatoa eruption as the likeky cause of a Bubonic plague outbreak which reached Europe by ship! Bing gives 536AD as a date.)
I remember this! In Cosmos the show with Neil Degrasse Tyson he mentioned that people who worked in optics and therefore glass often worked in puddling furnaces that gave off toxic fumes that would shorten lifespans. This may be the case with opticians.
Your comments about solving for Verdun's constant from a quantum basis reminded me of how empirical electromagnetism was done before we understood the structure of matter. There are theorems that show that as long as the "macroscopic" fields are small compared to the internal binding energies of the parts (atoms and molecules, natch), assuming a linear response to the fields will do just about everything you need. You can then "renormalize" the vacuum wave equations with tweaked, empirical constants with effectively no knowledge of the fiddly details.
This got science an absurdly long way before we began understanding the fiddly details. And note that it is an approximation. Crank up the electric (or even more difficult, the magnetic) fields enough and the technique fails. Still awful cool though. And it meant that experimentalists were able generalize from light in air to light in a vacuum with little effort - so useful.
At the time I think the Rosetta Stone had just been discovered and their was a race between England and France to see who could decode Egyptian Hyrogliphics. That meanappropriating and pillaging as much Egyptian cultural artifacts as possible. There were a lot of French soldiers in Egypt at that time, and disease ran rampant.
TIL that Egypt threw a shoe at Napoleon.
I worked in a thin film PV manufacturing facility as an engineer for about 3 years. We actually measured the thickness of our films using thin film interference. From the light that was emitted on the PV, some would reflect off of the film, and some would refract through the film and reflect off of the glass underneath the film. By measuring the difference in the two reflected beams, we were able to measure within a precision of 0.1 microns (the film was only ~3 microns in thickness)
History degree and I’m trying to understand the faraday effect but you’ve honestly just poleaxed my entire consciousness trying to understand how Egypt was like OIF or how Bush likens to Napoleon.
My colloquium for my second year undergraduate lab experiment which is on polarization is in two days. Thanks for the introduction to polarization!!!
I really like the idea of Faraday shining a laser through electromagnet (at 11:40). It shows how old I am. When I studied physics lasers were already used a lot but they still had the glamor of a new invention about them.
only 1 min old and already 6 downvotes. Peeps must have have STONG opinions about Faraday.
You can see the downvotes?
It's the buttons. They have the wrong polarization.
He literally wasn’t even a mathematician and nobody respected his work until Maxwell put his work into a language people could understand. He was basically a crackpot. Instant dislike. /s
Users cannot see downvotes
@@adjutantthere’s a plugin that lets you see them
One thing about polarizers I had trouble remembering from college was a detail about quarter wave plates, which have different indices of refraction along different axes. What I couldn't "reverse engineer" in my head is how a quarter wave plate of a particular thickness could do the same magic (say turning linearly polarized light into circularly polarized) on different wavelengths, when it seemed like the effect would be different for different wavelengths. Finally after years, I looked it up: they DON'T! The action of the quarter wave plate is indeed wavelength specific.
@Angela Collier, thanks for these. I didn't complete my undergraduate physics major, 35 years ago, but I have kept studying all these years, and I am still very much in love with the subject. "It's fine!" -- A. C., Ph.D.
I got a good chuckle out your total hopelessness during the "Experiment" at the end of the video.
the reduced power of 3 filters is not always reduced by a power of 8:
the transmitted intensity through all three polarizers is equal to the initial intensity (I0) multiplied by the cosines of the angles between each successive polarizer,
Angela Rocks!!!! and I have to thank her for making me ponder this aspect of physics. Gr8! Peace ☮💜
Holy cow, the chapters and notes! That’s gotta be a lot of work. Thank you for including that.
The Rumford medal is named after Benjamin Thompson, an American born scientist who became Count Rumford in Europe. Thompson/Rumford's story deserves its own video.
I kinda dozed off cuz I was tired but if it wasn’t mentioned, polarized light is how modern 3d movies work. Each eye lens filters a different direction of polarized light and the movie is played quickly alternating between two different types of polarized light.
Hi there, how does that make it look 3d then?
@@Amethyst_Friend basically creating the illusion of 3D involves having a different perspective for each eye, to do that you have to find a way to block the eye thats not supposed to see a given image from seeing that image when its up. They first did this with the red and blue glasses which would filter out the parts of the image that eye wasn’t supposed to see because each perspective was color shifted to only be visible through its corresponding color filter. When the first home 3D tvs came out, they got around the color problem (cuz it was annoying watching a movie color shifted) by making special glasses that had frame shutters that would physically block one eye lenses at a time, alternating back and forth 60 times a second, it was synched to the tv so each eye could only see the frame it was meant to, but this was still annoying because even though the illusion now worked with the correct colors, you could still kind of see the blocking of the frames and it was distracting. The technology wasn’t really practical until they realized they could use polarized light to filter each image to the corresponding eye. So they have two projectors (pretty sure) that each have a light polarizer on them but set to different polarizations and then the glasses have a polarized light filter that filters out the images that aren’t intended for that eye. The movie is played at 60pfs (again, pretty sure) but our brain only process images at 30 fps so it seems like a fluid 30 fps movie with each image arriving simultaneously even though it’s not. And the result is the illusion of 3D without the need of color shifting the movie or with overly annoying and expensive glasses. There are good videos on YT about it if you’re still curious.
@@Amethyst_Friend The same way colored glasses do. But instead of filtering based on color, the modern glasses filter based on polarization.
I think I get how the coloured ones work. The two different colours are slightly offset on the screen, which tricks the eyes into depth perception. If, as the OP says, the polarizing version of 3D quickly alternates the two types of light, is there also then a need to physically offset them after the same fashion?
Thanks@@Kycilak
@@Amethyst_Friend The offset is still needed as that is what tricks as into depth perception. The color in the colored ones just makes it so one eye sees just one (eg. blue) image and the other only sees the second (eg. red) image.
The polarized lenses just don't filter based on color, instead filtering based on polarization.
I actually used this effect on a research project in undergrad to try to measure the magnetic fields of galaxies [we didn't have the resolution in the end, but w/e]. Basic premise was to look at a polarized source behind the galaxy, and use the wavelength-dependence to determine the (integrated) strength of the magnetic field (along line of sight) despite not knowing the original polarization. That way we could determine at least the overall direction of the magnetic field relative to the rotation of the galaxy (which, perhaps surprisingly, isn't known). [This was radio data, so the wavelengths were long enough that effects were measurable.]
The wavelength dependence is that angle is proportional to wavelength squared, so the traditional way to do this is to fit a plot of angle vs. wavelength squared, assuming a single source. But we were trying a new technique, "rotation measure synthesis," which basically extracts the light emitted at each "Faraday depth" (magnetic field times length) using the fact that (1) rotations in 2D can be complex phases, (2) using that phase as part of an integrand Faraday depth and wavelength squared are dual under a Fourier transform, and (3) Fourier transforms are invertible [with some technical caveats, both the usual ones about finite data and the fact that wavelength squared is always positive].
Very neat idea; I don't know if they've tried to do it since (I left the project back in 2015 or so, and completely lost track since 2017 when I graduated).
You described Faraday as a “top-tier physicist”; I think everyone will agree we would love a physicist tier list video.
Yes! More demos please! They are fun to watch, and give a more visceral understanding.
I just read that the glass Faraday used to discover this was *_one third lead oxide_* (one third silica, and one third boricic acid). I don't know if these propotions are molar ratios, or volume ratios.
Previously, I said magneti-optical disks (like the Minidisc) used the Faraday effect, but I was wrong, they use the closely related Kerr effect.
Transmission through a transparent media is the Faraday effect, and reflection off a magnetic surface is the Kerr effect.
Great video! Love the experimental demo, always enjoy revisiting physics with your insight and humor. Someday i will understand these electro-magic waves 😊
I don't know if this will soften your dislike of "corpuscle", but it's pronounced like "muscle".
Same
Revolutionary French viewed warfare as an academic pursuit. They would bring scientists and artists with them to solve engineering problems and examine (pilfer) art. Being in campaign is bad for your long term health!
Also pre-revolution scientists were prominent noblemen and many didn’t make it through the terror like lavoisier.
@@danmccune5637All the people she mentioned died after the reign of terror...
That was the first time I've ever seen the Faraday effect actually demonstrated! Neat bit of work. Polarizing films or 1.25 inch eyepiece filters are probably still available from Edmund, and magnets you can get anywhere. That would be a fun thing to have around, then donate somewhere. I know a couple of teachers.
I would honestly love a series of videos that are just failed attempts to recreate old timey physics experiments, ultimately concluding that physics is just kinda hard, and people shouldn't underestimate the brilliance of the people who get laws, constants, and formulas named after them.
OMG, the audio is glorious! New mic day? Congrats!
Ok maybe it wasn’t the most polished physics demo, but I thought it was really cool and would love to see more in future vids!
during your digression about Faraday's light source, I recalled that he lived during the heyday of limelight. now, im saying he used limelight to stare directly into - it is intensely bright - BUT, wikipedia does give this tidbit:
"The limelight effect was discovered in the 1820s by Goldsworthy Gurney,[4][5] based on his work with the "oxy-hydrogen blowpipe", credit for which is normally given to Robert Hare. In 1825, a Scottish engineer, Thomas Drummond (1797-1840), saw a demonstration of the effect by Michael Faraday[6] and realized that the light would be useful for surveying [...]"
Your videos are the best! Polarized goggles & sunglasses for snowboarding, polarized filters for my cameras (which are so cool because they have 2 pieces, the outer one rotates & one rotates it to be able to eliminate reflected light from glass or water so as to to see what's on the other side of the glass or water & it also makes the sky incredibly beautifully blue) & I've always wondered about the physics of how that works.
I never ever looked it up because I had a feeling that eventually the answer would reveal itself to me.
And through you, Angela, it has. And I thank you so very much for that.
Again, I think your videos are absolutely wonderful and I cannot thank you enough!
It's always a pleasure to see a video of yours Dr. C!
I'm glad you swung to the right in your shot, it was bugging me the whole time whether or not that black book with the red band was Just My Type or not. Also, I'd read Maus before, but I finally picked up both at a sale recently and it's a delight to revisit. Maybe "delight" sounds strange for the content, but you know what I mean.
Your physics knowledge is impressive but it’s your honesty and passion that brings me back for more.
Love the video, some of the most informative science I've seen in years, and the history lessons are fun to boot. Even the parts where you slip up or are unsure are charming in their own right. It's honestly very refreshing to see that experimental side of things, and to see a real and relatable reminder that this stuff is complicated, confusing, and that demonstrating it can be hard. Too much of what we have available to us today feels alienating in how refined and perfect the end results present themselves. It seems easy to feel inadequate in the face of all our collective discoveries, and the painstaking efforts of those with the resources and facilities to consistently reproduce their effects, especially when we only ever see the finished products for demonstration.
9:00 pronounces like Hoi-gens. Not to be confused with that other fellow, Kai-per. :)
The part at the end trying to manually hold a laser and also a laser in water has big "Slotin's screwdriver" vibes. Being scared was a very reasonable feeling!
I love that you incorporate the history of science and don't just explain how things work.
I think of my self as at least some what scientifically literate but I've never heard of this experiment. 15:40 Gas Light 1792 , Lime light 1826 Thank You!😃
So in this vid, I found myself near the start going, 'oh, funny way of thinking about light, ok, I'll start getting my head around it', only for you to half way through go 'it's not right', but then not offer a replacement understanding. So in the end, I came away knowing the experiment, and the results, but I didn't come away with that normal deeper understanding of 'why' things are happening (that your other videos have been so good at leaving me with)... Hopefully this comes across as helpful feedback as opposed to criticism or some such btw. Always love your vids, but yeah, this one just felt... A little more like a history lesson than a delve into physics?
What a perfect time for this video to drop, the semester just started and I’m taking a lasers class as one of my major electives
I barely understand any (read: none) of that, but your excitement/tendency to jump between unrelated thoughts made my ADHD brain very happy XD. Prob gonna go rewatch the video tho to make sure I actually understood at least some of it.
Paris in 18 and 19 Century had a lot problems with poor water supply and hygiene related diseases were rampant, plus between 1780 and 1850 they had a revolution roughly every month and by 1870 the Prussians were sick of French wars and captured the city after a long siege.
19:30 note that life expectancy is a misleading statistic! even in ancient times, if you lived to 16 you were extremely likely to live into your 60s. the number is driven down due to infant and childhood mortality from disease
Median life expectancy at birth would paint a much clearer picture, but I can't find those figures anywhere. I'm not sure why life expectancy is usually measured as an average/mean.
The frenchmen were likely dying younger due to some combination of more densely packed cities, worse sanitation in those cities, particular local pollution types based on industry, diet (don't forget how much butter French cooking uses), military service, casualty in regional conflict, and a scoche of confirmation bias (e.g. you just haven't found the scottish physicists who died young yet).
New microphone?
I spent more time trying to get the microphone to record than i did trying to get the farday effect to pick up on camera. May have been a mistake since you are the only one to notice.
No, it's very noticeable. Just make sure it is not a French microphone.@@acollierastro
@@acollierastro it's one of those things that's easier to notice when you go back and compare. sounds better and there's less echo for sure
Microphone is great
this experiment was the first experiments that really excited me and blew me away during my grad school photonics course. since then I've been obsessed with photons and things like fiber optic gyroscopes. physics is cool :)
Yoooo I noticed and appreciated the increased audio quality this episode
Wake up babe, new acollierastro video just dropped.
"What is going on" in early 19th century France is best answered with a sad look and a puff of smoke.
So nice to see a theorist show some love for arguably the greatest experimentalist of all time. He was not much of a mathematician, but his discoveries were the foundation for what Maxwell took and formalized mathematically. There is almost nothing in modern technology that wasn't a consequence of those two men. Angela's fumbling with her experiments is kind of funny but highlight the need for people with the hand/eye coordination to meticulously setup and perform these experiments. I to am amazed at what scientists, 150+ years ago, were able to do using only hammers!
One thing he apparently failed to discover, or that he was maybe slow about, was safety glasses. He apparently blinded himself multiple times - I recall picking up a book that had some of his letters years ago and flipping it open to see something like "I have to apologize for not having written back sooner. The [I don't recall what] exploded and I was blinded again for several days." It's the "again" part that got me. But yeah, he did a huge amount of amazing discovery.
@@chrisl6546 Well he was hardly alone at not taking proper precautions -- example: the Curie's.
This is actually kind of a good companion video to LowSpecGamer's video about the development of liquid crystal displays. He didn't really drill down into the physics so much since he's more interested in the manufacturing and application in consumer electronics.
The existence of top tier physicists implies the existence of a physicist tier list and I feel the viewing public is owed a glimpse of Dr. Collier’s work in this area
This video is actually top notch UA-cam. Amazing.
First, as an experimental physicist, I want to thank the author for trying to reproduce the experiment with the Faraday effect. Most theorists do not realize how difficult it is sometimes to do something that is described in a hundred words and a couple of formulas. Secondly, the field of 50 microtesla is negligible for most practical applications. It is very funny to hear about such a "huge field" when people on earth create fields of hundreds of teslas, and inside antiferromagnets there are compensated fields reaching about a thousand teslas. Thirdly, I am a stupid experimenter, and so far I cannot find an understandable quantum description of the Faraday effect. That's why I was very upset that you specifically missed this part in the video. In conclusion, the geometry in which you applied the neodymium magnet to the Faraday cell corresponds to the magneto-optical Coton-Mouton effect, which most likely influenced the polarization.
“What’s going on in France!? . . . Quantum, quantum, quantum!”-Dr. Angela Collier, PhD, theoretical physics, UA-camr
"Whatever, it's fine" is definetely catching on as a catchphrase.
'All I know about magnets is this, give me a glass of water, let me drop it on the magnets, that’s the end of the magnets,' Donald Trump.
Well well at 13:55 , I could definitely see you as a Victorian era steampunk physicist! Living to be 100 years old, of course ;)
I know you most likely won't see this. However, you have quickly become my absolute favorite science communicator. Fantastic work
Riemann died of tbc at 39 too in Germany
Hope you were wearing safety specs when using that Amazon green laser. As Brainiac75 demonstrated, the cheap and nasty ones leak infrared and lie about their power rating. Brainiac75 also does experiments with very strong magnets, and wears gloves to protect fingers when handling them.
It turns out that although mantis shrimp actually can't see many more colours than we can they _can_ see UV and circularly polarized light which is pretty cool.
In France it was easier to become a scientist as a commoner/middle class than in England (in that specific time period (after Napoleon, before WW1) where being a scientist was mostly reserved for the aristocracy/upper class. Higher the class = lower chance of dying early.
When it comes to math and science I’m at sea until somebody explains the *history* of how a concept was arrived at. Once it becomes part of a story I have a much easier time comprehending it.
Wave equations are hugely important once we get Maxwell's equations. Maxwell turned Faraday's work into something able to make usable predictions. Made electrical engineering a thing. - You got to that.