Electron Mirror - F-J's Physics - Video 131 

If you put one coil on the back and a very powerful magnet in front you can get the beam to spiral like a tornado. If you get a old radar detector it will also make microwaves that can set it off. ❤

Christopher, have a look at this video of mine where I show helical electron beams! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9QmeHCw6pN0.html

Cannot thank you enough for your work, and letting us enjoy it. One of my new favorite channels. Please keep em coming!

I will - now no promises but anything you would like to see that is within my 'simple' bounds? I did get asked for the Tennis Racket Effect in some comments a while a go so I did make that one!

Thank you.

That's facinating! Not sure if you mean cathode rays or the actual electron mirror demonstration. If so you must have been one of the very lucky ones to see this demonstrated and what a great instructor/teacher you must have had therefore. Funny how these things can have a profound effect on us, one others would just not see at all!

I think these demonstrations are so important. The first demonstration I saw was lead iodide precipitating. Two clear liquids making a yellow solid!?!?. I've been studying chemistry for 25 years and I'm still fascinated. It's all magic :)

Yes, we must never forget that these things can have a wonderfully lasting and positive effect on youngsters! You have to start somewhere! We all remember growing crystals too!

Dave, well remembered! A couple of things - did you really manage to do Millikan's exp? That is a nightmare to do in a school lab! Secondly I think you used a different tube for your e/m which makes life a lot easier. Did you use this tube instead (hope the link works) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_1y_-BeCAHQ.html

Anthony, yes it was exactly the same JJ Thompson apparatus we used so its been around a long time. I was convinced that the formula for the magnetic field through the Helmholz coil would come up in the A level exam so I committed it to memory. Sadly I can’t forget it after all these years and the damned thing still haunts me. We all did the Millikan drop experiment in the school dark room as it was very difficult to see through the microscope into the oil drop chamber with a small lamp shining through it. I remember the oil aerosol squeeze bulb, which was a bit like my mum’s old fashioned scent bottle. The equipment was pretty antique and it was tricky to balance the voltage to get the falling droplets to hover, especially in the dark whilst peering down the microscope but we all managed it. The physics teacher who was amusingly called Mrs Jean Scull - you can imagine the nicknames the poor woman had to endure along with her hubby, the school’s history master, but she was brilliant. She plotted up all the results for the two experiments on the blackboard as bell graphs and worked out the mean and standard deviation in her head - no calculators or computers in those days only 4 figure log tables for the plebs (us) trying to keep up. The result we got for m, the mass of an electron, was well within a standard deviation of the published value from the National Physical Laboratory. At the time we were being groomed for the new frontier of nuclear science and engineering and we did loads of other experiments using equipment and materials that today’s kids wouldn’t be allowed to go near never mind play with. Mind you when we asked Mrs Scull whether it would be a good idea to go into the nuclear industry she said that if we did we should start a family early. I decided that mining engineering was a much safer option.@@AnthonyFrancisJones

Thanks Dave, that's a fascinating story and you are probably one of only a handful of people (alive) that have actually done Millikan's experiment. I have a piece of school kit in my loft which is used to simulate it to avoid all the hassle you went through. I should get it out. Sounds like your science teaching was outstanding. Those 'determine the...' type experiments seem to have gone these days and I must profess that all my teaching was 'don't worry too much about the fine detail and actual result - can you see how it would be done and how it all works.' True of many of the videos I post here! I guess you are familiar with all the fudging of the figures that Millikan did and the issues that caused for many years after. Talking about nominative determination, our physics technician was Mr Brain. Thanks again for taking the time to comment. It is amazing how many really interesting comments the videos have got recently - makes it all worthwhile and adds to them greatly! Hope you enjoy some of the others and do let me know!

Scott, fantastic to hear from you! Yes, I don't do the 'it blows up' stuff! Others do that well. Interesting how many of the viewers of this video did not realise the importance of a very high internal resistance EHT supply to make it much safer to work with. I fear current more! Thanks so much for your fascinating story. I was doing similar things in the 1980s and I begged my dad to buy me a CRO (Hameg 203-5). Every kid should have one! I felt I could have been there with your dad as I remember the smelly process of etching PCBs myself. Worked really well. Remember the UV light box? It was only years later I realised that there was HP stuff out there with incredible measuring resolution and I have some examples now. It was a real pleasure to hear your story and it took me right back to my childhood workshop in our old pony stable. Thanks so much for watching and sharing too! An example of what RU-vid does best!

Haha less Medhi or AvE More like Applied Science, Alphaphoenix or Clickspring

Isn't Applied Science amazing and he does it without any fuss at all - amazing!

Thank you! Yes, I was so lucky to have some of the best teaching in the UK at the time. I have to thank my parents for that too! Thanks for watching and taking the time to comment.

Pleasure and glad you found it interesting. I guess you have seen my other cathode ray videos as many of the tubes I use have a low pressure gas in them making the beam visible - just what you don't want in a regular CRT!

My word! To be included in the same breath as those other channels! Thanks and glad I produce something that you like and interests you! Hopefully more to come!

Fantastic story and thanks for sharing - sounds like we had very similar experiences. It certainly shows the importance of being around the right people who will support your interests when you are young - and yes, it is not normal for a young teenager to demand a CRO to play with! Glad you had/have a great dad and that you also had an excellent physics teacher. In my experience we do it because we love to share what we know rather than it just being a job! Thanks again for commenting! BTW my 5 year old loves playing with my Hameg CRO - nothing digital - just a good old analogue CRO.

@@AnthonyFrancisJones I think it was a Telequipment CRO, one of the ones with the black outer and red inner knobs. Definitely analogue. It was a two channel model and had external trigger capability. Not sure whether it had x-y mode though because I don't remember making Lissajous figures, which would have been an obvious thing to try. Fond memories! P.S. All my science teachers (including Dad) were great.

Yes there were lots of those scopes around and many in educational fields where Tektronix was more for professional applications (and big money too!) BTW I must do a video on Lissajous figures. Been meaning to for a while but working on one on Lorenz Attractors at the moment which uses the CRO in a similar way. Great to hear you had such brilliant support as a child. It is really important!

Thanks Tony. It is a good starting point for focusing in an electron microscope which of course can then display on a fluorescent screen. I have not seen this experiment done before so I thought it was worth demonstrating!

Umm, why not dredge up an old CRT display? Though admittedly, this is better for display purposes

David, yes I could but it is not so easy to demonstrate the electrostatic bit of the deflection so this tube is purpose made for education to be able to apply both E and B fields. Perhaps your suggestion could be another video of mine at some stage.

@@AnthonyFrancisJonesThank you lol, I forgot that the beam deflection on a CRT is the deflection from two magnetic fields. I used to have an ancient oscilliscope 35 years ago (WWII era?) that did this with an electrostatic field in the Y axis. all hand soldered discrete components on holding cards. still perfectly functional for what it was. My folks threw it out while I was out of the country, considering it "Junk", not knowing it was a very valuable antique even then

Interesting David. I still have a valve Cossor CRO - no way that can be thrown out as you could not even lift it! I seem to remember it does not have a single electrolytic capacitor in it which shows quite some design! If my channel went more the 'Big Clive' direction I would take time to feature all of these old bits of kit I have!

You see he will make black hole like all scientists messing with long tubes of particles .

@makeshiftlabs3083 Many thanks, it's a small channel but I am glad of your support!

Thanks Matt and so glad you liked it! It is a great piece of kit that has probably been totally forgotten!

Thanks - glad you liked it and found it interesting. Yes, lots of uses especially in electron microscopy.

Thanks Shawn! That's really kind of you. Glad you enjoyed it. I have a few more Tetron videos 'in the can' which I will publish soon. Thanks for watching and taking the time to comment too.

Thanks! Glad you liked it. It is a fun demonstration and so few people have seen it! You are right - lots of physics concepts in this one!

My pleasure. Thanks for taking the time to watch and comment.

Thanks! I completely agree with you. I often look at the still pictures I took of these experiments and just marvel at how beautiful they are (the interaction of the electrons with the atoms of gas in the tube).

My absolute pleasure. Thank you for supporting this small channel!

Thanks Jonny. Yes, looking at the magnetic field especially as the flyback is not electrostatic. You might enjoy my Electron Gun video if you have not already seen it. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_CsLU-1VGug.html Thanks for watching and taking the time to comment.

Thank you! Glad you liked it!

Thanks for this - all excellent comments! Yes as the magnetic field is across the tube and the electrons passing through it at 90 degrees over this small distance (at the velocities they are going at) it looks like they are 'pushed down' but of course if the magnetic field was stronger they would twist as you say into a circle as explained in this video of mine ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-7hJxn4l47X8.html I have perhaps over simplified 'curl' for the sake of an accessible explanation. Agreed too that there is a change in velocity so the loss is only in one direction not a loss in speed. Thanks again for taking the time to comment. I really valued the input! Hope my explanation does not 'grate' too much!

Thanks and glad you liked it.

My pleasure! Good to see your flying. We share a hobby there though mine is a bit more noisy! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ZvlxJ1oLCb4.html

Thanks Jozef. Glad you found it interesting!

With the right set up you would see this effect. You might want to look up synchrotron wigglers which act in a similar way!

You are right - but it was great to get a chance to show it to you and others on RU-vid. Thanks for watcing!

Good question - with the right field shapes this would happen. You might be interested in the 'wiggler' in a particle accelerator (synchrotron) which is not that dissimilar and results in a spectrum of synchrotron radiation. They use Halbach effect magnets for the magnetic field, which are really interesting so you might enjoy this video of mine too: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LgJR4nYKKJ8.html

They generally cope but I tend to only touch the connectors' fatter plug insulation and, the power supply of course, is of extremely high internal resistance.

Thanks for commenting. I must do a demo to show there is no x-ray worries at some stage. Forgive me for doing this but I copy another response I have just typed and hope that explains it. I am, however, very grateful to hear from you. "Good question. Firstly these tubes are designed for school use with safety in mind. Secondly we us a very high internal resistance EHT supply and finally x-ray production is not really an issue for voltages as low as used here. However, we have to risk assess using CLEAPSS, and their advice too is that there is no known risk. Now, there were rectifier tubes in TV sets that did have an x-ray risk associated with them, I have one, and it needed to be used with some screening. Thanks for asking - you make a very good point!"

Thanks, it is a great and rarely shown demonstration!

Thanks Robert - Glad it helped!

@@AnthonyFrancisJones To understand something helps to build a foundation. Now I want to learn more. You are a gift to science and education seekers. Enjoy your weekend.

Robert, that is very kind of you. I had great teachers at school and all the way to Cambridge. I have been lucky that I enjoy communicating ideas which seems to be my thing rather than high level physics research! Hope you enjoy the other videos, suggestions welcome. I had someone suggest the Tennis Racket Effect a while a go which was a fun video to make, and thanks for your encouragement.

Yes, Jon. Not far off. Have a look at this video of mine which does the cathode ray (TV) tube in more detail ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_CsLU-1VGug.html

Thanks. Yes, many schools had/have them and may well have them hidden deeply in a forgotten cupboard. Mine are about 40 years old. The stands are really heavy but you have to take them out of the stand to pack the tube away in its polystyrene packing case. That's when it can all go wrong!

Good question. There are distant similarities in that a TWT uses an electron gun and beam of cathode rays. However, wound around the beam is a wire that has an RF signal in it. The magnetic field due to the RF signal does indeed 'shape' the electron beam and this can lead to signal amplification. So in the respect of electron beams and interacting fields there are some similarities. Thanks for watching and glad you enjoyed the video!

Dale, some things just remain beyond the realms of explanation!

Pleasure Mike and thanks for watching!

Thanks. Hope you continue to enjoy the content and thanks for the support of my small channel.

Rudy, not sure I understand your question. The electrons are produced by the cathode? If you mean the plates the electric and magnetic fields are set up so they are deflected before hitting the metal. By the way have you seen my flying videos? ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ZvlxJ1oLCb4.html

Yes, they always make and appearance - stops me from taking myself too seriously!

Yeah I do believe any time there’s a vacuum it definitely produces x rays too, good question

Good question. Firstly these tubes are designed for school use with safety in mind. Secondly we us a very high internal resistance EHT supply and finally x-ray production is not really an issue for voltages as low as used here. However, we have to risk assess using CLEAPSS, and their advice too is that there is no known risk. Now, there were rectifier tubes in TV sets that did have an x-ray risk associated with them, I have one, and it needed to be used with some screening. Thanks for asking - you make a very good point!

Joonas, that is a brilliant question. I believe the magnetic field has to be much stronger. In this case it is due partly to poor electron beam focusing and by poor electron velocity selection. So there are a range of velocities experiencing different deflections. Hope that helps and thanks for watching.

@@AnthonyFrancisJones Thanks for quick response! Although your explanation seem plausible, I’m not convinced. Shouldn’t what you say result in smooth output instead of so clear splitting? The same was classically expected for the Stern-Gerlach experiment and led to the discovery of spin-based splitting.

Thanks for getting back to me. Well spotted, there is a really clear gap in the velocities or at least the paths of the electrons. Interesting! I need to do a calculation (you might beat me to it!) to see what magnetic field strength would be needed to show the splitting and also I believe the separation in the SG experiment was very small too. I must look at the tube again. I don't remember seeing it. It has been suggested that the ripple on the EHT power supply could have synced up with the camera frame rate. That would be a really lucky coincidence. Good to keep us thinking!

Good questions. The velocity selection of the electrons is not very good in this very simple electron gun. We also feel that ripple on the power supply does not help. There may be other factors at work here too. It is not connected to the speed of light - the electron velocity is controlled by the strength of the electric field (or accelerating anode voltage). Secondly, you cannot accelerate electrons faster than the speed of light as it would need an ever increasing energy source. Energy input and corresponding velocity are not linear especially close to the speed of light. Another way of thinking of this is that due to E=mc^2 the mass of the electrons would increase needing ever greater energy to speed them up further. Zero velocity electrons if not in a field will indeed accumulate until they repel away. Or of course will flow to ground if there is a conducting path for them. Hope that helps a bit and thanks again for watching! Oh BTW did I see a Clansman C320 in one of your videos? I remember them really well from my youth and the C349 which I was always repairing!

@@AnthonyFrancisJones Thank you for the answers and clarification! This helps =] Yes, that is a C320, and I use the primary on CW Night at the end of the year. It’s a nice radio to have and listen with =]

Great - C320 takes me back to my youth as a cadet. We had all that kit!

Thanks Paul. Thought it would be interesting to show the interaction of a E and a B field. Yes, I have to be careful with the wires but as I have said before, years of practice, the room looks much darker on the video than it really was and mainly these 'educational' EHT supplies have massive internal resistance so risks are greatly reduced. It's the van de Graaff that I don't like! Thanks for watching!

Not a dumb question at all. Normally the tubes (like in an old TV) are evacuated to remove all gas particles at they scatter and effect the beam focus. In these tubes we need to be able to see the beam traveling so it has a small amount of Hydrogen or other gas in it and when the electrons hit the gas they ionise it. This (by recombination of the an electron back onto the gas) releases the energy it gained in the ionisation as a photon of light. Hope that explains it! Good question!

Thanks Jacob! Glad you liked it - makes it all worthwhile!

Well spotted! No I did not turn anything off. So the beam is only visible when it hits the phosphorescent screen and when I disconnect the top wire I think the presence of the negative bottom plate skews the beam out of the way a bit so most of it misses the screen - you can still see a bit of it going straight. Once I remove the electric field due to the bottom plate then all is well again and the beam goes directly to the right. Great question and well spotted!

@@AnthonyFrancisJones I think you need to investigate this a bit deeper. I personally have a lot of issues with the knee jerk off pat answers that are repeated so easily because you have been told how it all works so many times. But there is still some wiggle room left for doubt I think. There is a whole lot of such experiments that are always interpreted in only the one way, with little or no critical analysis being employed. For instance, Thompson "discovered" the Electron. But he actually discovered nothing at all. He only surmised that if there were such a thing, then that might explain what he saw. Rutherford never "discovered" that the atom had a nucleus, and most of the atom was mostly empty space. No, he deduced this, not discovered it. That is why experiment can be used as proof of theory, only possibly supportive of a theory. So then, what might be the reason why the "beam of electrons" suddenly just magically disappeared just because you removed that top electrode? Something unusual is happening, what do all those authoritative text book have to say about this effect? Is it even mentioned? My gut feeling is that what you are looking at is not even "a stream of electrons" at all. When you place the magnet near, the "stream" curves off.. toward the bottom or top of the tube.... but as electrons are particles (that's the CLAIM anyway) so where do they all disappear to once they have struck the sides of the glass tube? If you leave the thig working for 10 years, do you see a little pile of dead electron particles built up at the bottom of the tube? I recon that there is something fundamentally incorrect with some of our assumptions and deductions about all this. Our imaginary Model of it all is able to help us use electricity, but the model may not even represent reality at all, but still be useful. What do you think? Can you do more experiments looking for any slight inconstancies to the official consensus? Another issue I have is the claim that we have actually fired a single electron form an electron gun. Or counted a single electron with a detector, or done this with Light photons, which are imaginary particles as far as I can see. Lots about approved Physics is a bit dodgy.

Interesting what you say. You would enjoy a philosophy of science course at university if you have not done one. You get the gist of the 'scientific method', no 'proof' but models that help us understand and assimilate what we see around us. Further experimentation will always lead us to new/improved models. Proof is not really what we deal with as you say. What I would add is we do need simple models that are quite limited to teach beginners and younger pupils. 'The electron is a negative particle that can be found orbiting a nucleus' etc. later on quantum ideas need to be added to, as you say, explain unusual effects that we observe in further experimentation such as orbital energies and spectral lines etc. The 'kids model' works for my 5 year old and is not wrong - it is just limited. Separately you ask what happens to the electrons that strike the glass etc. of the tube. Well, I cannot prove it, but the model that we use is that the glass does have some conductance (some glasses are actually lead glass) and this allows for the electrons to have a current path to ground. Then we get into the realms of the Earth's capacitance... Some tubes had an aquadag (graphite paint) on them to help this. So it is all about using the appropriateness of a model to the age and ability of those that you are explaining it to. A bit like teaching planets to little children - one has to simplify the orbits into something they have experience of such as circles knowing that in the future they will not find that completely wrong but will develop it in a number of different ways to explain further observations. I have had criticism over the years from some quite famous physics educationalists for doing this but I have not found a way around it. What it all comes down to is this video should really just have been a string of maths of quantum particles and field interactions with no demonstration but I feel it adds something to the story even if it is a bit 'handwaving'. If you do have some further suggestions about how I might teach this to school age kids I would be really grateful - it all helps!

@@AnthonyFrancisJones No worries. I understand your approach. Thanks. Actually my main gripe with modern Physics is the very real issues that exist for the Einstein theories of relativity and also of Quantum theory for that matter. These particular theories, especial relativity, is full of so many contradictions and simply totally irrational statement and assumptions that its bewildering why its still being taught. Time dilation, length contraction and gravity waves, Light speed, unbelievable. There is so much fake science that it hard to find real science these days.

I am not sure if there are many of us either in our out of University/school teaching that genuinely wish to deceive our students. We just want the best for them. Quantum theory as well as Relativity are really tricky concepts that are not fully unified yet and may never be. The main thing is we explain to students that the maths of these theories can be used to genuinely describe many systems and allow them to build others too (I am thinking particularly of some electronics applications). Obviously when there are gaps in the theory more work needs to be done and still is being. We are nowhere near 'knowing' all of the science. What I find hard to explain to my students in the philosophy side of science is that the fact that there is no fundamental law that states that if the human brain cannot visualise something it does not mean that the model is wrong - one has to go with the maths that makes the right predictions or modify it so it makes better predictions. One of my goals with younger students is to give them the science models that enable them to get to grips with something they have not seen before. When they are older, of course the model has to be extended/modified or completely changed! In summary I do hope that there are not too many real scientists out there peddling 'fake science' and if they are they will fall on the sword of failed predictions and outcomes. I suppose in summary what I am saying is that as scientists we can only give models that enable us to try to understand outcomes and make predictions. We are not about 'The Truth' only a Theory that seems to currently fit the situations in front of us. We are short of so many of these models. Descriptions of the universe's structure on a cosmological level is definitely one!

Interesting David. Not a field (no pun intended) that I have experience of. From what you say I am going to have to return to university to restudy physics all over again - getting a bit old for that but sorry if you feel my explanation misled you in any way. If you have an example of this experiment done in the way you suggested please do let me know.

Sadly (or perhaps it's a good thing) not a hope for the very reason you mentioned. Electron beams being charged (like alpha particles too) are highly ionizing so any air in the way would stop the beam over a very short distance. It would of course not even begin to penetrate a wall. Now a gamma ray or neutron source would be a completely different matter and are a real nuisance in the nuclear industry as they need really dense and thick absorbers. Jury is out on H Syndrome but high power microwaves would not be at all nice as would be subsonic sound. I forgot to say that any charge on the human body would immediately flow to ground so they would remain neutral anyway!

Yes, that's right. It is referred to as 'an electron mirror' as it is a way of getting electrons to deflect in a similar manner to light off a specularly reflecting surface. In short it is the technical name for this process but of course there is no physical mirror as one would imagine involved!

@@AnthonyFrancisJonesthanks for explanation. May I call that deflection and not refraction?

Yes, that is the best term I guess - as you said it is not really off any solid object but rather deflection by the combination of fields.

That's a really good question and well thought out. Sadly the answer is 'No' and equally sadly the reason is not at all easy and involves using relativity to look at what is meant by moving charge which is a bit beyond me in a comment. Simplifying electrons as balls of charge that move in wires does not really stand up to this type of analysis. To give you an analogy - not a particularly good one - if you wave your hand about, even though the outer electrons in your atoms are shielded from the nuclear charge quite well you do not emit electromagnetic waves. The understanding of this is really quite difficult and beyond normal high school teaching. Sorry for such a poor explanation but you have hit upon a really good example of where simple 'charge moving' models break down. Thanks for watching and taking the time to comment.

Thanks Leonhardt, it is always great to have examples from people who have worked in the field (no pun intended). Yes, isn't it interesting that young people would have no idea why a 'screen saver' is called a screen saver these days! I remember seeing burning into the phosphor on the CRTs of ATMs (cash machines) as they often had green screens with very fixed images. When doing the electron diffraction demo (have you seen that video of mine) it is very easy to burn a hole through the graphite target/sample too. Thanks for your insights and also for watching and taking the time to comment.

It is wonderful isn't it and I love the colours too! Charged particles ionising gases do show some really artistic effects!

Thanks, I had a look and could not see that bit but if so one does need to be careful. As I have commented elsewhere I am using an incredibly high internal resistance power supply with this in mind! I must say that with good current sources I was always taught to keep one hand in my back pocket at all times! Thanks again for watching!

Yes, I think the velocity selection at the anode is not that good in this type of tube too but I did not check the power supply for ripple either - they are generally quite good as the current is so low but school kit...! (Oh, of course the filament is AC too, as you know, and so there is a little bit of voltage variation there as well).

@@AnthonyFrancisJones Thanks for replying. That's also a good point, although a filament thermal inertial should smooth it out a bit. That reminded me of an interesting observation using DC on direct heated cathodes. The potential gradient across the cathode means it doesn't emit electrons evenly and over the filament length. Not something I had though about.🙂

Yes, that's a good point! There will be a difficult to model thermal gradient/variation on the cathode. Trouble with physics, the deeper you dig the more complex it gets! I must get some of my other Teltrons out. I need to do one with the Perin Tube at some stage and possibly a triode as well. A few of the tubes I have are damaged (not by me) which is a shame but they are great when working.

@@AnthonyFrancisJones The Perin Tube is another great tube and thought provoking when compared with the diffraction tube. They are all somewhat delicate and easily damaged but glad you still have a few to demonstrate.

Must get on and do the demonstration. It is a bit of 'What to do with the tubes when I am done?' though!

Colt, I am not sure that I get your question but I think I do so... this only works with streams of charged particles, in this case electrons, so you could not deflect the light from an LED if that's what you mean. Regardless, thanks for being so supportive and I will of course produce more videos soon and I hope you like them. Do keep commenting!

I want a single shot or maybe a double. Not a machine gun

So this device fires billions of very low energy low mass electrons along its length which is why the device at the start of the tube is called an electron gun. It only works in a vacuum too as even air would stop the accelerated electrons. This video of mine might help you understand it better. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_CsLU-1VGug.html Hope that helps. Firing single electrons is really tricky and the quantum nature of the particles really shows up then making things a bit more tricky!

I have not demonstrated the double slit yet. It is not easy to do with electrons but a simple laser pen and some very narrow slits work well. We used to scratch a couple of slits with a razor blade onto a blackened piece of glass. Easy to do but take all the precautions that are sensible when doing it please!

Good question Peter and your explanation is good too. These systems set up field shapes that have the effect of 'velocity selecting' electrons or other charged particles so that the beam contains only one energy. My tube has a range which is why the beam spreads in the fields. You might be interested in looking up synchrotron wiggler - an interesting device that does behave a bit like my demonstration here. Thanks for watching!

@@AnthonyFrancisJones Do you know what my device is called? Google hasn't been helpful.

Peter you are probably thinking of a 'Gun Solenoid' in a e RadioFrequency Photo-Injector which CERN use. All a bit technical!

Yes, it perhaps reminds you of the northern lights.

Yes that's right which is why the force on the electrons becomes less as they slow down even though their charge remains the same. And as you say it is proportional F=Bqv. As far as the 'mirror' goes hope you don't mind me pasting one of my previous answers: "However, this experiment is referred to as 'an electron mirror' as it is a way of getting electrons to deflect in a similar manner to the way light would off a specularly reflecting surface. In short it is the technical name for this process but of course there is no physical mirror involved! It has many uses but especially in electron microscopes to guide the beam." Thanks for watching and taking the time to comment. F-J

@@AnthonyFrancisJones HaHa, as I imagined- in most of the nomenclature is either done by non scientific people or before they have fully understood the phenomenon. But they always stuck to that. Thank you for explaining personally. It is not everyday I get to see an electron gun.. really enjoyed that. Please keep enriching our knowledge and experiences.

My absolute pleasure and glad you are getting something out of it all! Richard Feynman used to complain about people who 'hid' behind nomenclature without actually explaining what it meant. At times, I seem to remember, he would pretend to not understand the simplest bit of physics if it was presented to him in a jargonistic way - wise man and educator!

Good question - it is called this as it is a way of directing electron beams as if one had a mirror there. Obviously that works for light but not electrons so we use external magnetic and electric fields to have a similar effect. Hope that helps!

I believe it was said somewhere below ‘...referred to as 'an electron mirror' as it is a way of getting electrons to deflect in a similar manner to light off a specularly reflecting surface. In short it is the technical name for this process but of course there is no physical mirror as one would imagine involved!‘ a commentator said it was more deflection than defraction.

Yes, that was me!

Gosh that's going back a bit Gregg and I am not sure we had it in the UK.

Steve, thanks for your excellent question. Do you mind if I copy a previous response of mine: "Normally the tubes (like in an old TV) are evacuated to remove all gas particles at they scatter and effect the beam focus. In these tubes we need to be able to see the beam traveling so it has a small amount of Hydrogen or other gas in it and when the electrons hit the gas they ionise it. This (by recombination of the an electron back onto the gas) releases the energy it gained in the ionisation as a photon of light. Hope that explains it! Good question!"

Good question. The electrons come off the negative cathode and feel an electric field attracting them to the anode as you suggest. However, this field causes them to accelerate to very high velocities. The anode is hollow so they 'overshoot' it and pass through the hole in it making them free to travel along the tube. This is the basis of how an old cathode ray tube TV worked. You might find this video of mine explains things a bit further. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_CsLU-1VGug.html Hope that helps.

thanks for answer!@@AnthonyFrancisJones

Interesting point. The electric and magnetic fields on the sun's surface do indeed direct plasma in a way that leads to some interesting shapes. The sun's magnetic field is responsible for interactions with charged particles that are moving and therefore a current creating a magnetic field. I have done a video on Helical Electron Beams which may be of some interest therefore. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9QmeHCw6pN0.html

@@AnthonyFrancisJones Earth's teluric currents appear to look similar too. (Rather interestingly heraldic suits of armour appear match these field lines.) I have to confess to being a proponent of the 'Electric Universe' and therefore your demonstration is much appreciated. Cheers.

Interesting. I have not studied Plasma Cosmology in any detail and would probably need to return to postgraduate studies to do so in any detail (is my maths up to it now??) though I think my university studies are well behind me! It is interesting just how many models there are out there. String Theory was the big field of study when I was a student. More videos to come and thanks for watching!

@@AnthonyFrancisJones Would you mind commenting on something for me? Purely non committal aka 'We won't take you away' but I'd appreciated your thoughts on the following: An astronaut outside the atmosphere, floating through the medium of space would be physically incapable of seeing a single one of the billions of known stars, moons or even giant sized planets, due to our lacking an atmosphere for the photon to collide with. No collision results in nothing to see, you see! Two astronauts tethered together would be invisible to one another, it's bizarre but true.

Interesting - so I will do my best to explain. If you see dust in a room in the air when sun shines through a blind or smoke in front of a film being projected that is because the light from the projector reflects off the particles and into your eyes. Yes the actual light rays or beams are not visible directly (nor does quantum electrodynamics allow for their existence but ray theory helps younger students to get started). Now to the astronaut problem. We place telescopes such as the JWT and Hubble etc. into space as the light they pick up is much clearer without the distortion in the atmosphere (similar to the dust in the room or smoke in a cinema). So in space you get an even better view of stars etc. as the light goes directly to your eye/retina to be processed by the brain. So in summary the less collisions there are the clearer the image. I hope that answers your question. Remember my demonstration tubes basically had vacuums in them (like space) but you could still see all the components inside! Hope that helps - physics is never easy but you chip away at it!

Good point - I would like to say that years of experience of this type of apparatus and most importantly a very high internal resistance EHT power supply make things pretty safe. But, yes, you need to know what you are doing and why!

@@AnthonyFrancisJones Sure, driving without seatbelt with a lot of driving experience keeps you out of danger. Or, so they say.

I was wondering what the insulation rating was on the ultor wire and connector.

Probably not high enough Tom but it has always been a standard school experiment and I have never been zapped - check for nicks in the insulation though. One does need to be careful!

Yes, you are right - they say this incorrectly. I would not trust the mechanics of the car or the other drivers to start with, so I always wear a seatbelt! With this kit carelessness would lead to problems and the biggest one is dropping it on the table and getting glass flying about! I do make sure that the internal resistance of the EHT is in the mega ohms so that tends to keep things in check! Have you seen this video of mine where I connect a 1.5V lamp to that power supply? ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-V06sYBiYWqM.html Hope that helps!

Indeed but still very relevant especially in the case of some electron microscopes!

Yes! Lots of similarities here to the old CRT TV. Have you seen my other videos using these Teltron tubes? If not, do look them up!

Yes, I take your point Brian! Thanks for watching and hope you found it interesting!

Interesting point - it is of course the electrons that play a major part in specular reflection in a regular mirror if that's what you mean. However, this experiment is referred to as 'an electron mirror' as it is a way of getting electrons to deflect in a similar manner to the way light would off a specularly reflecting surface. In short it is the technical name for this process but of course there is no physical mirror involved! It has many uses but especially in electron microscopes to guide the beam.

Thanks for this observation - could you kindly give me a time stamp of where I say that - am am struggling to find it, but perhaps I did let a slip of the tongue get through. I would be very grateful. Thanks, F-J.

@@AnthonyFrancisJones 9:30 you say curve back to the negative plate at the bottom, but the wave curves up to the positive

Thanks and well spotted! You would make a great student with attention to detail like that! You are of course right! Thanks again for pointing this out - it was not an easy video to make! Many thanks again.

@@AnthonyFrancisJones Your video is excellent! Very impressed with your equipment, you basically made a oscilloscope for measuring electron waves. People never believe in something they can't see, I invented a 219 year rechargeable lithium battery and the same process made single use lithium batteries rechargeable for free, can't see it working without a voltmeter, so no one believes me. I do own a business in the tasks of me you seek, I often work for free and/or profit sharing. I am seeking investors with selling legal company shares in my company for a international patent fee of $5,000 Canadian dollars, I am the next Nikola Tesla forced to dig ditches, while I have a new battery energy source design in my back pocket. Most don't understand patent law, can't make any public income without patent on the battery technology or I never get one. Thank you for a reply, its a super complex area of science, I only know because, I am professionally trained by my local university, I have spent my life in this electronics industry, I am that one in a billion person that would notice a detail like this. Feel free to ask me anything, I am a ham radio operator, I like to reach out to people around the world, just to hi.

Thanks and hope you continue to enjoy the videos I produce!

Yes, one has to be very careful using the word 'exist' as a physicist. I use the electron particle idea as a model here of course. Going for a more quantum mechanical approach would not be quite as accessible to my audience as the maths has to do the talking. It is an interesting point you make - how do you explain this experiment to your students? Any pointers will be gratefully received.

Thanks Anna. Yes, I did not want to get too technical and I am not sure others would have the kit to copy what I am doing but at the beginning I hoped I did explain where each wire went. By all means ask me if you are not sure for your studies. As far as the voltages are concerned I make sure I have years of experience and training and know the apparatus very well. But... the main thing is the high voltage power supply has a massive series internal resistance - that is the key to safety! You might like this video where I am 'mad' enough to wire it to a 1.5V bulb! Knowing your physics I guess you know what I am up to! Tell me what you think. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-V06sYBiYWqM.html