Applied Science - 2015-07-27
See how olive oil and magnets can control the brightness of light via the Faraday effect. Get your iron-on Applied Science logo here: https://www.patreon.com/AppliedScience Measure Verdet constant of olive oil: http://www.sestindia.org/wp-content/uploads/2013/12/Volume-2Number-3PP-362-368.pdf Plastic film polarizers: http://www.apioptics.com/linear-polarizers-spec.html Faraday effect: https://en.wikipedia.org/wiki/Faraday_effect
This takes me back to my undergrad physics days. We had this one lab experiment where we measured the deflection of a laser beam shot through a relatively small chunk of faraday rotating material like TGG, YAG, and an ampoule of olive oil. The entire setup was done in such a way where a change in polarization also result in a change of the angle of deflection of the outcoming laser.
The setup was basically a cylindrical blackbox with a slot for the material in the middle, a miserable circular compass angle measurer at the end, a laser at the other end, and both cold water and 4kV coming into the black box. Scary magnets, so we had to make sure we left our wallets and phones and watches well away from the setup.
In the end we spent 3 hours measuring sub-degree changes in deflection, getting mad at the small thickness of the faraday rotator, and using all our skills in error analysis techniques to get a calculated Verdet constant within the correct order of magnitude. It was fun times and typical for an undergrad physics lab with equipment older than the instructors.
Then you come over going all "Hey look at this faraday effect in a clearly visible way, isn't this cool?"
You're doing good work.
The Fifth Walking Way I really like your story of undergrad physics, and it sounds a lot like many teaching lab exercises that I've endured as well. I agree that most of the descriptions and teaching labs on the Faraday effect are way too esoteric and seem to miss the idea of giving folks an accessible understanding of how the universe works. It makes me want to shout at professors, "Just explain it, will ya?!"
***** Perhaps you're new here. As you might have noticed, the comments sections on my videos are free from hateful and unproductive talk. Please do not force me to start deleting comments. Having a decent comments section is rare on the internet.
+Applied Science as a high school physics teacher, one of the things that I struggle with is making things accessible to students. one thing i like to do when I can is build experiments with home materials, or send students home to do their own. I have had students do this with electroscopes, but it is hard to find experiments like this that can be even partially home-made. Good work!
It's hard to make things accessible to students, not because they are stupid, but because you're dealing with about 10% of their attention on average.
I have that video. I love it.
Wow, Memory Lane: My friend Earl and I did this for a High School physics project about 41 years ago. We built a cell similar to yours wrapped in a big coil of copper wire that was connected to a high power vacuum tube amplifier. My recollection is our cell was filled with glycerol. We sent the beam of a He/Ne laser through the cell across campus and speaking into a mic connected to the amp sent voice messages (one-way) to a phototransistor receiver. We also experimented with optical crystals of potassium aluminum sulfate cut along different crystallographic axes, I still have these crystals but I don’t recall the results. I believe there is a Scientific American Amateur Scientist article but haven’t found a reference to it. Cheers, Mark
Mark Beeunas Good stuff!
Mark Beeunas
PS: Can anyone find the Scientific American Amateur Scientist article that shows this experiment? I'm pretty sure there is one.
Cheers,
Mark
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Mark Beeunas 41 year agos high school experiment? wow
Mark Beeunas -- You might be thinking of "How to construct an magneto-optical modulator" in the Amateur Scientist column of the November 1970 issue of the Scientific American. However, I believe that that column treated a Kerr cell rather than Faraday rotation.
Good on you for leaving the magnet accident in, as a reminder/warning to others; That even pros underestimate those little devils sometimes, and it's all over in a fraction of a second. (Hope you didn't get hurt. Done it myself.) And thanks for the demo!
I work with rare earth magnets all the time but much smaller ones so when I make a mistake like that no one gets hurt. It just destroys $100 worth of magnets and hours of work. Little, brittle bastards.
Electro Boom Moment
Your "accident" with the magnets was AWESOME. I almost had soda come out my nostrils when that happened. Science is dangerous, but funny!
USWaterRockets And remember: science is not about "why?", it's about "why not?".
USWaterRockets lol Last time that happened to me, they exploded... "Why would you ever need safety glasses working with magnets?" I'm glad I have an addiction to safety glasses.
One needs to be very careful with powerful magnets. They tend to pick up each other very far. I usually never like the idea of free magnets while moving another. Hand can be drawn to something like iron very quickly when you hold a big magnet.
frtard I have a thick set of leather gloves I use with them too. I got pinched by two magnets like this on a finger tip and it was like getting pinched in a pair of pliers!
USWaterRockets People are so used to the regular 'black fridge magnets" which have barely no power that they simply can't grasp how much more powerful neodymium magnets are. A fridge magnet can lift a few grams of iron. A neodymium magnet the same size can lift a few kilograms of iron. You can buy neodymium magnets that can lift 200Kg, and it fits in the palm of your hand.
THe distance at which they attract is also much much larger than compared to the regular fridge magnet.
Maybe in order to get 45 degrees of rotation, you could have a long array of coils perhaps around a pvc pipe filled with water or maybe even a flexible fiber optic! Awesome video as always!
Very cool effect. The faraday effect is also used to measure current in a high voltage power line of aHVDC power station, they wrap a fiber optic cable around the cable and I guess measure the amount of polarization change which is proportional to the magnetic field and thus the current in the cable.
That blows me away. Other than liquid crystals I had no idea there was another way to modulate like like that without actually changing the light source. The optical rectifier is a cool concept as well, you make me wish I was home with my basement lab full of gear.
Nick Moore
Then be ready to be blown away again. Ever heard of the electro-optic effect? Can do the same thing, but by applying a voltage to a crystal instead of a magnetic field. It's much faster to control (coils are hard to drive fast because of their inductance), you just need to be able to move charges quickly (like in any piezo). Crystals exhibiting this effect are used in telecoms a lot, where optical switching in the GHz range is needed.
Weird, I have some Googling to do. Thanks.
Absolutely fantastic and I am a long time electronic circuit designer who says that. I have not done any research on this subject yet but it looks like you have something worth exploiting other than on Youtube. Thanks for uploading a well done video.
Cool set up. I suggest you use three different lase pointers (red, green and blue) on a colored liquid (engine oill) and measure the amount intensity of light with and without the Mag.field. Your demo is excellent. I have a couple of publications on Mag CD. I wish you could demonstrate the Kerr effect, reflected light on a magnetized surface. Note: polarizers give you circularly polarized light.
Hey Ben, been following you for a few years now and really enjoy your videos. Though your questions video got me thinking that it would be cool if you did follow up videos on projects you think had significance or that gained plenty of attention/questions.
Anyway, keep up the GREAT work!
I hope you never give up on Youtube, Ben. Your videos are a fairly unique asset.
You just answered a question I have had for years: how did the ferrite rotators work that changed the polarization of an X-band radar wave 90 degrees with a simple, dc input. Some second-generation airborne weather radar systems with parabolic antenna dishes (e.g. Bendix RDR-1) had a grid made of metal wire perhaps 2 mm in diameter, across the upper portion of the parabolic dish. In weather mode, a "pencil"-shaped radar beam was required, and polarization of the beam was maintained by waveguide to be in same direction as the wire grid, passing through to the parabolic dish to focus the beam. In map mode, a fan-shaped beam directed downward was used to map, or "paint," ground targets such as coastlines and cities. Selecting map mode sent a dc signal to a unit called a ferrite rotator on the antenna feed horn, activating a magnetic coil and rotating the waves so that they hit the grid and deflected downward, effectively changing the shape of the dish. Now, many years later, I learn of the Faraday effect, which is, I suppose, what made it work. Later radar systems use flat plates to shape the beam, ruling out use of a grid. I believe that another method of shaping a map beam was developed for use with flat plates, but that was after my time.
Канарев Ф.М. - Дифракция фотонов.doc - https://cloud.mail.ru/public/Lspd/4PEoBcYQN
«Канарёв Ф.М. - Фотоэффект.doc» - https://cloud.mail.ru/public/6gr4/yzMs4fVGM
Канарев Ф.М. о взаимодействии спинов фотонов.doc - https://cloud.mail.ru/public/9yWt/xdGqj1ysU
Канарев Ф.М. об Эффекте Доплера.doc - https://cloud.mail.ru/public/EAgw/BEoyxvVvC
По следам эксперимента Баранова-Зателепина , 12 августа 2019 года https://drive.google.com/file/d/1QsUVE55DRhdoR32kdaXusBYhbRZ16b4-/view?usp=sharing
I've seen the Faraday effect in a clear medium rotate different wavelengths by different amounts. The effect on white light is very colorful and beautiful. Photo diodes are good for sensing changes in the max intensity point. But the human eye is superior tool for observing the intensity minima.
Great experiment !
You could also try to use a series of toroidal magnets such as the ones used in micro-waves ovens
I know this is an old video, but I thought that I would give this a go with a pair of 40 x 20 x 10mm thick N42 Neodymium Magnets, but I've had no noticeable effect on olive oil, where the video shows it visibly working on water. I've used a different amount of spacers to to match with the description around 4:42. I even added a 3rd magnet to extend the lines further. I also tried a polarized 50 mw 650 nm lazer, as the verdet constant is dependant on the frequency of light, and I was able to all but extinguish this much light with my polarizers crossed, so any change would be quite pronounced..
I am trying to work out what I have missed; any ideas?
You're videos are amazing! Thanks for your hard work. My favourite educational youtuber by far.
That was very interesting. Thank you for the great videos. I've learned several amazing things so far in the short time I've been aware of your channel.
Ben - great video! Microwave systems use this effect (Faraday rotation) for circulators and isolators.
Amazing, I can't believe I've never come across that effect before. I might have to do some calculations to figure out what it would take to get a 45 degree rotation.
Mind blown, I have wondered my entire life how to make a real one way light 'check valve', I concluded it couldn't be done because anything done to the light would be commutative, I am astonished this can be done.
Uhh wouldn't a one way mirror do that?
@⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻ ⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻ One way mirrors aren't actually one way. Light will still pass through both directions.
@⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻ ⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻⸻ I guess one way mirrors take advantage of our eyes perceiving different contrast levels
Classical light effects are typically modeled using matrix multiplication, which is definitely non-commutative:)
Very cool, I learn a lot from your videos. Question, if you increase/decrease the current is there any change to the observable light,will it correspond to current?
Thanks a lot.
Thank you for putting that incident into the video, it can show people how even experts can injure themselves with these objects, it's a good reminder for everyone to be cautious coz your dealing dangerous stuff..
I don't know how practical it is but a magneto-optic Kerr effect microscope would make a great project. Viewing the actual magnetic domains of magnetized objects would be fascinating!
Thank you for your interesting experience. Explanations and demonstration are very well done.
Interesting. The application you mentioned is like a diode. It also looks similar to a transistor, in the sense that the application of electricity looks like a junction gate.
I build an electrical polarimeter in school about 24 years ago for chemistry. I used a large coil and had a special glass rod made by Schott from a glass type called SF-59, 10cm long, about 2cm diameter and polished super-parallel planes on both sides. I still keep the glass for sentimental purpose. If you are interested, I could lend you the glass rod if you want to extend the experiments. It was in the days back then the material with the highest V (0.128 arcminutes/gauss*cm, water has 0.0131) without gaps in transmission in the visible spectrum.
This channel inspires me in ways I can't even translate to words. Thanks for the great content!
Hi Ben. Is it possible to use specific rotation as a one direction light filter? Camphor has a specific rotation of 44 degrees due to its chiral nature.
I'd love to see a light diode with permanent magnets even if it only dimmed the light a bit more in the blocking direction.
Another fantastic void. I wish that I had know of this when I was in school, would have made a great science project.
I'm wondering if a reverse effect could be seen. If a powerful light was projected through the coil, as you did, while a very steady and very preciously measured and monitored current was flowing through the coil and the light was then switched on and off, could there be an effect on the current flow though obviously very, very small?
It world be cool to try this experiment with an MRI machine. You can't turn the coil on and off but it's probably strong enough to see the effect where it's clean on a direction and dark in the other
In high power laser optical isolators (device to stop reflection back to laser source) we use TeO2 as a crystal material, you can get the 45° or more this way. We put a polarised beam splitter in as well to put the waste energy out into a beam dump, because at high power you will break stuff. I blew holes in PBS already. And another material that's over 2000W/mK xD
Can you try this with a much smaller permanent magnet or much larger polarisers, or perhaps just move the camera closer? To visualise the felid lines all the way around the magnet, like a better version of using iron filings on a sheet of paper.
we did this experiment at the university when I studied physics 25 years ago. The effect we observed was much less because of less perfect polarizers. I would not have guessed that you can see it this clearly even in water and olive oil!
What you demonstrated with the 45 degree polarizers is a light diode. As an analogy with electric diodes, the optical polarizer lets light pass through the material in one direction but not in the opposite direction. I can't remember the details, but this has applications in laser technology.
Excellent video and the extra information on shape of the permanent magnet fields is very helpful.
Now use it to play with quantum entanglement! Just need a laser and crystal (photo multiplier would help too I guess.
Maybe see if you can get one stream of electrons to pass through an anti-polarized filter by changing the orientation of the other stream of electrons? Changing one should affect the other right?
Same effect that makes microwave YIG oscillators/YIG filters work. Nice to see it in optical domain, too :)
Hi Ben, nice video. Before this video I did not know that there is some kind of valve for the light also. One of friend and I was wondering is there any such kind of valve for heat also
Can polarized lenses be used to direct dim (randomized) light to straight light so that you can use the light through a focusing lens and heat things up for example?
Matter is held together by monopoles the individual N and S magnets. Electron is not the charge carrier in electricity, there are 2 particles involved. Awesome video.
Did you personally design your "new" logo? It's really good, without being OTT.
Great video.
Interesting thanks :) I actually thought it was only certain materials that did this. This is nice to know
I want to try this with a large rochelle salt crystal. Rochelle salt rotates the polarization of light, and I have a funny feeling it would change a lot with the Faraday effect.
Not that I want to see you hurt or anything but I burst out laughing when you accidentally brought the magnets too close, then backed the video up and burst out laughing a second time! Great video, I think I'm going to play with this myself, maybe see if I can wind an electromagnet specifically for this task. Also, the iron-on transparency looks cool and all, but I really want a sticker or two! I collect them on my toolbox.
elektro3000 Stickers would be awesome.
elektro3000 I plan to make Applied Science stickers for the next subscriber gift. Thanks!
This YouTube channel is unique. High quality camera, good voice, and cool experiments.
05:40 very good explanation of magnetism using paper, pen, props and innovative camera shot. Very good work bravo.
Great video. Your channel is wonderful. Keep it up!
Any thoughts on how this could effect fiber optic communications?
Physics Videos by Eugene Khutoryansky - 2015-07-27
Great video. I would like to mention that the reason that the polarization of light is affected is because the speed of propagation in the material is different for light polarized in different directions, and this property of the material is influenced by the magnetic field. Simply just having a magnetic field interact with the light will not do anything, since light is itself just an electromagnetic wave, and the constant magnetic field from the magnet would just add to the electromagnetic wave through superposition.
Flounderhouse - 2018-01-30
Eugene you are just wonderful.
Ku龜 - whaleturtle3。Tâibûn台文 - 2020-11-15
:10
FJ S - 2022-10-24
Ben explained this, stop trying to steal his audience. It's so obvious what you're doing.