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.

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

Your "accident" with the magnets was AWESOME. I almost had soda come out my nostrils when that happened. Science is dangerous, but funny!

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.

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.

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!

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.

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.

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.

Very interesting video. Well done as usual.

I hope you never give up on KZfaq, Ben. Your videos are a fairly unique asset.

A well-done, easy to see and well-explained demonstration of a somewhat obscure but fascinating phenomenone. Kudos.

This channel inspires me in ways I can't even translate to words. Thanks for the great content!

This KZfaq channel is unique. High quality camera, good voice, and cool experiments.

BUT WAIT THERE'S MORE!

I really like the drawing on the paper on the table to explain.

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 KZfaq. Thanks for uploading a well done video.

*Heavy Breathing* I've been waiting, Ben

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.

Excellent video and the extra information on shape of the permanent magnet fields is very helpful.

This is a great video. Your enthusiasm is contagious.

nice production! great phenomenon... and that "oh snap" moment is an instant classic XD

This is one of the coolest videos you've ever made!

Hey, our university professor showed your video while teaching the Faraday effect.

Thank you for taking the time to make this awesome vid

Excellent demonstration! I'm going to be doing this asap.

It is so cool to see this in practice.

05:40 very good explanation of magnetism using paper, pen, props and innovative camera shot. Very good work bravo.

amazing quality of the video and the script!

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..

Whoa glad your fingers are okay. Your "beep" actually censure beeped my verbal response perfectly.

Excellent presentation! Thank you.

Thank you for your interesting experience. Explanations and demonstration are very well done.

Ben - great video! Microwave systems use this effect (Faraday rotation) for circulators and isolators.

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!

Such a great detailed video. You are legend

Great video. Your channel is wonderful. Keep it up!

subbed. cool video, seemingly cool channel. i like the white paper, really good idea for a clean background. will redo this at home with some old glasses from the cinema

Very cool video. Love this channel.

A really good one, I have a some polarimeters at work to try it myself

Keep up the awesome videos.

I just discovered your channel. Excellent videos!

I'm definitely going to have to try this one for myself.

awesome job, best video pertaining to faraday effect on youtube

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.

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.

It really opened my mind...thanks...

I absolutely love this channel because of non-trivial content. Does anyone know any other similar youtube channels except for sample-eater Cody's?

You are a champion. I love you vids.

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.

This is so cool!

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!

Great video and presentation. And those magnets add quite the element of surprise!

Same effect that makes microwave YIG oscillators/YIG filters work. Nice to see it in optical domain, too :)

I found another favorite nerd! Nice vids! Thanks for sharing!

Interesting thanks :) I actually thought it was only certain materials that did this. This is nice to know

Dude I just bought the same bench supply as at 0:38! At least it just came in the mail, I ordered it so and so days ago. So funny I just watched this video!

This video was worth it for the near finger mashing alone! :P Learning more about the Faraday Effect was good too!

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, thanks for sharing.

I really enjoyed that thank you.

Hardly related but I picked up a "copper" version of that Ikea lamp over the weekend, love it haha

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!

thanks for the video, really informative

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.

Nice video!

I love how your distilled water has an MSDS warning label XD

Excellent and Very Interesting Video! mate.Very Thanks For Sharing :)

The Kerr effect, mmm that reminds me of using 2 photon lasers. Your vids are great and so educational!

You have the coolest gear. I want your lab.

Wow! Great video. You introduced me.to photo diode !!

Great experiment ! You could also try to use a series of toroidal magnets such as the ones used in micro-waves ovens

When you were discussing the non-return beam filter it reminded me of electro-chromatic mirrors, aka "dimmable" mirrors, in some cars.

Similar effect was used as a shutter for ultra fast photography of atomic explosions in Manhatan project. The camera is called Rapatronic.

Very interesting, although I'm still a bit confused about what light polarization even is. I'll probably just read a wikipedia article about it or something, but in my mind, it's weird how light has a certain polarization angle while it's direction of travel never appears to change.

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.

great info , tnx !🔬📉📐📚⚡

thanks for sharing this it was very interesting

Can you do this reverse? So that normally both polarizers block light and when electromagnet is turned on it pass light , is it possible Really amazed by this experiment, nice explained!

There is a story that Tesla once made a source of light that seemed to come out of thin air between to large metal plates he was using with a coil setup. It was mentioned by an eye witness during his years around the world fair. No one to this day can replicate what he did. The last mention about light reflections being influenced by electromagnetism has me thinking.

That Ikea lamp though. So useful.

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.

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.

Eres un campeón... Felicidades amigo gracias por tus videos

This effect was not covered in my physics university curriculum as far as as can remember. Quite surprised to learn about it.

Awesome!

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

holy crap ! I allmost fell out of my chair when the magnets jumped together :-)

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.

wow, thanks for this videos...

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.

Thanks for your wonderful video. Would you please tell me which type of bobbin did you use in this experiment(The number of coil turns)

I wonder what would happen of you gota fiber optic cable and looped in thorugh the coild multiple times

Marvelous

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.

I didn't know about this light behavior, although I've heard of the Zeeman effect from my astrophysics book.

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?

Ben, you make some of the most interesting videos! Cool name too! ;-)

Interesting!