The humility you bring to these videos where you're willing to ask for explanations and admit what isn't your forte is really inspiring and makes some pretty esoteric stuff a lot more approachable.
I can't say I understand this enough to explain it, but 3blue1brown has an excellent video correlating quantum tunneling (via the Uncertainty Principle / Unsharpness Relation) to a Fourier analysis. Whether true or not, it helps me make sense of that and the "infinite sharpness" required to make waves simply start, end, or turn 90 degrees without side effects. I believe this is also made more explicit in another video I can't readily find. th-cam.com/video/MBnnXbOM5S4/w-d-xo.html
“Unlike a ball, we can’t pinpoint exactly where an electron is.” Wow, balls must be really good at physics to be able to pinpoint exactly where an electron is.
Cats are inherently non-classical objects [1]. My cat can move through a closed cat door, but he never does so when I'm there observing him (he just meows for me to open the cat door). Is it possible that he has harnessed quantum tunneling? [1] Schrödinger, 1935
I think quantum field theory might help with intuition. Instead of thinking in terms of particle vs wave you can view everything as disturbances in fields. This means that particle behavior arises from interacting perturbations in fields and the interactions of different “particles” or a complicated multiple perturbation event can create a field effect without the particle seeming to cross that distance. Really the move from thinking of particles and waves to considering fields was a huge moment for me!
@Anzu Shiina Perhaps, but some infinities are bigger than others.There is an infinite quantity of whole numbers. There are half as many odd numbers, though there is an infinite quantity... th-cam.com/video/elvOZm0d4H0/w-d-xo.html Edit: series=quantity
@@Pekkhum Well, technically there are not infinities bigger in quantity, but there infinities of superior order (which contain numbers that other infinities does not).
I've often heard that quantum tunneling 'sometimes happens' when the energy potentials make it possible, but not about the evanescent wave function. I'm very glad to have learned something today. Thank you so much for taking it a couple steps beyond what is so often repeated, while keeping the math accessible to non-physicists.
I love your honesty and references to previous videos, it shows you analyse past experiences, take on board feedback and aim to create a more efficient future with more understanding examples 😊
Thank you for this. I've never encountered a description of quantum tunneling that made the remotest bit of sense to me. This gave me what I can comfortably say is a vague understanding, which, considering it's quantum physics, is high praise :)
fortunately I don't have that problem since I just assume they are both cylinders with zero radius and infinite length. The perks of being a physicist...
@@achyuththouta6957 Seriously though for a moment, not necessarily. It could also approximate a cylinder with a very small radius and large height in some situations. Such as trying to find the electric field inside a cavity.
I may know why that drop of light occurs. Like when we throw a ball on floor it reflects. In this process it losses very little kinetic energy to floor . Thats why we feel vibration in floor during the process. Now imagine ball as a wave of force. This wave will reflect like a ball at a certain angle but very little wave will pass through floor. Now this may what is happening with light. When it reflects some of its energy or em wave passes through the surface . And thats why we may see a drop of light...
Tunneling is also a term in game/physics engines which describes when collisions are missed because the simulated objects are too small and too fast. It's a result of simulating things in discrete timesteps (two objects might only be colliding for half a timestep), and I think it's named after quantum tunneling.
The e^(-x) function approaches but never reaches zero. Does this mean that quantum tunneling is always possible, but just increasingly improbable, for any non-infinite potential barrier?
First, does QM applies to non-subatomic particles as well, like people? Second, does that mean there is a non-zero, though perhaps 10e-100, that I am actually at you house, which sounding from you name may be in Erupoe, er Europe?
I suppose that if one is made of 10^25 particles or thereabouts then there is a reasonable chance that a handful of their particles have tunneled away from what one considers their body, for certain definitions of "reasonable". But the remainder will be at about where they are expected to be. I used to have a sign on my bedroom door that read, "This may be that one in a trillion chance that the atoms of your body align perfectly with those of this door, and you can walk right through it. Go ahead. Try it."
Yup!!!! It could, in theory, tunnel in an amazingly great distance, just be extremely unlikely to do so. E.g. if the barrier is 1 m thick, and the tunnel constant is about one per nanometre (just as a very rough for atomic scale), then since 1 m = 10^9 nm, you get tunnel probability on the order of e^(-10^9) ~ one shot in 10^434,294,481 - a number that is so large, at over 434 million digits - that simply writing down its _digits_ would fill many volumes, to find it tunneled in by that highly-macroscopic distance. That's _hundreds of millions_ of _orders of magnitude_ less likely than winning the lottery jackpot every single drawing for the rest of your entire life _and_ getting hit by a bolt of lightning every day _and_ surviving each and every strike _and_ randomly encountering every single last famous person on the planet every day _and_ going to beers with each and every one, all in the same lifetime. Indeed, it is so fantastically unlikely that we could say with extreme confidence - enough to bet all the money on the entire planet and it'd be a _very_ safe bet with no foolishness whatsoever - that an event of this probability has _never occurred once in the entire history of the known parts of the universe_ .
Jade, you asked for an explanation to evanescent wave decay. A good example is to look at ocean waves. Near the surface a measurement of the hydrostatic pressure varies in proportion to the varying wave height above the point of measurement. As the point of measurement goes deeper that point is no longer merely affected by the wave directly above it but by the combined effect of waves to either side of vertical. Assuming the waves are sinusoidal the average effect upon the variation of hydrostatic pressure tends to diminish as the contribution of multiple peaks will tend to cancel the contribution of multiple troughs. There is also a diminishing effect as you get farther from the wave due to depth (I suspect proportional to 1/r where r is the distance to the wave). There is a formula which describes the variation in hydrostatic pressure due to the waves as a function of depth, and lo and behold just as in the case of the evanascent wave that variation decays exponentialy. I am a retired sonar engineer, and this problem came up in the course of my work.
Hi Jade. You alluded the continuity of evanescent waves at around 5:49. Fundamentally in nature, there are really no abrupt changes at things with boundaries--it's exactly what you are explaining when you described non-infinite potential wells. You have to have a matched boundary condition and the natural way that happens with optical materials is to have an exponential fall off. I think you can look at it as a photon having a physical extent in that is has a spatial wavefunction associated with its position. As the photon approaches the boundary in the glass, the wave function of its position crosses the boundary and extends outside the boundary. The shorter the wavelength of the photon, the more confined it's likely position is and the faster the evanescence wave (field) strength falls off on the other side of the boundary--the wave number gets larger with photon energy causing the field to fall off faster. Thanks for making videos on this stuff.
Actually, there are no laws that forbids discontinuity, and they do occur in nature, for EM wave propagation in particular, even though E and H are continuous across boundaries, D and B can be discontinuous. Discontinuity is particularly prominent in phase transition and quantum mechanical phenomena like the photo-electric effect and laser pumping, where there's a threshold on the input parameters which triggers a different behaviour once it is crossed.
I'm not a physicist but a mathematician, so I'm curious about this. How can B possibly be discontinuous if you need to be able to take its gradient, curl and time derivative in order to even formulate Maxwell's equations?
Time derivative isn't really a problem since the discontinuity is only spatial. For the gradient, well, the component of B perpendicular to the surface actually has to be continuous, while the parallel component doesn't have to be, okay, so you might still not be able to take the gradient, but we're physicists, and we're allowed to just switch to the integral form when we want, and you can take the limit as the surface of the integral approaches 0 if you want to be all rigorous. For the curl, well, Maxwell's equation is written in terms of the curl of H rather than B actually (except for non-magnetic material where B = H) so it's fine there as well. Although, formally we consider the perpendicular and parallel components separately and take the limits as the line integral shrink rather than explicitly taking the derivative at the boundary. If you don't like the whole limit thing, you could of course fiddle around with weird functions like the Dirac delta which is obviously discontinuous but is defined to have an integral and derivative. But that's a bit much for a youtube comment and a bit out of my comfort zone tbh. I guess I have to correct myself, I misremembered before but technically all of E,D,B,H can all be discontinuous. However, Maxwell's equations do force certain components to be continuous across the boundary.
Cool, thank you for taking the time to type out such a detailed answer. I was suspecting that it would be something along the lines of switching to integral form or working with distributions, which don't have to be functions at all (such as the Dirac delta). Maybe at some point, I'll find the time to delve deeper into physics and will then remember your comment ;)
I am a 1st year engineering student and I missed the lecture on wave function. But YOU came to my rescue and helped me in that . VERY VERY THANK YOU . 🎈🎉🎈🎉
Because of the Wave function , quantum mecanichs is stuck for 100 years....Now people see the need more and more to just get rid of the wave function , like the ones that are interested in quantum gravity , or quantum information..... For me wave function is something that DOES work for things that are emergent.....when you go deeper, something else must replace the wave function.. Its the same like F=ma work... but for relativity not..... Everthing is emergent if you loock hard enough and every emergent thing has his own "wave function " --meaning the thing that describe the best....for the electron its the wave function....for the apple , planets , its F=ma... The next step after the wave function I believe that its information....
What wave function its for physycs now is what Newton gravitys was for Einstein back then.....something old, ineficent , that cant explain the whole picture.... There are many scientists that loock into this .... Try to search for your own on this matter. The wave function its not how Universe works !
If you search quanrum computer then you will notice that the whole ideea its to just bypass the colapse of the wave function using something deeper : information. Outhers try to baypass the wave function using mathematical shapes .... There are many approaches for this subject. But its something that everyone knows by now : Wave function it is not fundamental.
@@cazymike87 what are you talking about? Name me a reputable physicist who is suggesting to get rid of the wavefunction. If you get rid of the wavefunction you completely throw out all of quantum mechanics. Moreover, quantum computing's foundation is the wavefunction and entanglement of quantum states.
!!! You gave me an "ah-ha!" moment of my own! A few months ago I was researching equations of state, specifically SAFT. It basically models the molecular interactions between particles. I came across certain potentials and what not and it all made enough sense for me to at least conclude that the potentials affect the strength of interactions. Fast forward to today and here you are explaining what a potential well is and I'm like "OH MY GOD! THATS IT! THATS THE THING!!!!" You do amazing work. Keep it up and thank so much for that wonderful moment!
Some of questions. 1) does the energy of the particle in the wave function determine how long the evanescent wave will last? 2) If the energy of the particle does contribute to the duration of the evanescent wave, is there an upper limit to how long the evanescent wave can exist? 3) does the material that the evanescent wave travels thru effect the duration of the wave? for example can an electron tunnel thru 1mm of paper, but it couldn't make it thru 1mm of lead. (a millimeter is a huge distance for an electron, so assume I am smart enough to know the correct units of measurement ) 4) does the mass of the particle in the wave effect the length of the evanescent wave? Would a photon evanescent longer than an electron (all other things being equal)?
1) & 2) This is the time- _independent_ problem - so no relevant notion of "lasting" here 3) Yes; in QM lango, we'd model the lead wall as a _higher_ barrier than that associated with the paper 4) Yes; the wavelength is inversely proportional to the (square root of) mass (but notice that, although related to the exponential decay term in the barrier, in that region that term is not actually a wavenumber k (k = 2*pi/wavelength) )
I have a more complete answer to 1 and 2. The wave function inside of the barrier is exponentially decaying. And this decay is directly proportional to the energy. The more energy the particle has, the greater probability it has to tunnel through the barrier. Of course, this is only for the case when the particles energy is less than that of the barrier. If this condition fails, then tunneling doesnt occur because the particle is free to easily overcome the barrier energy. Then the wavefunction is oscillating, not decaying. But this is unrelated to the time. If youre thinking at this high of a level, I challenge you to just look at the solutions. You should be able to understand it
the wave doesn't stop at any distance just like how the function e^(-x) approaches 0 but never quite reaches it. So a electron could travel through 10 km of solid rock it just has such a tiny chance it probably will not happen before the heat death of the universe
A good way to Intuit quantum tunneling (for me anyway) is to imagine a wave (of water) breaking on rocks. Some of the water jumps the rocks and ends up on the other side. Wave mechanics is (for me) very intuitive if you visualize the waveform as a literal wave made of a fluid (the water analogy also works for GR and the warping of spacetime if you include bubbles in your visualization). Hope this helps in some way
@Razvan J the indivisible particle (quanta) IS the wave, so of course it passes through entirely, that's the meaning of the word "indivisible" Also the details are in the mathematics. This is about a way of picturing the mathematical results in your head. Still gotta actually DO the maths
@Razvan J that's your opinion and you're welcome to it. I shared the mental imagery that I personally use to make sense of the mathematics. If it doesn't work for you, then you're more than welcome to come up with your own mental imagery. However once you've done the maths a few thousand times the picture you have in your mind doesn't really matter anymore because it'll be replaced by the mathematical model and you'll gain a natural (mathematic) intuition for it.
@Razvan J the wavefunction of an electron occurs in something called a Hilbert space. The modulus of the wavefunction squared gives you the probability density of the particle's physical location. Sometimes that probability distribution extends beyond the initial boundary conditions which are imposed on the equation, and therefore the probability that the electron will be found outside the boundary is non-zero. Using a macroscopic wave is the method by which my brain naturally puts all that information into a picture. That's all. Like I said the details are in the mathematics, and without the mathematics the entirety of quantum mechanics means exactly nothing.
@Razvan J from textbooks and lectures, and I didn't HAVE to learn quantum mechanics, I chose to. The reason you have to do the maths a bunch of times is because it's the language of QM. Much like how you can't read a book until you have gone through the alphabet a bunch of times and know what all the letters are.
Jade these continue to be wonderful to watch. Clearly lots of people agree with me, which is reassuring. "Evanescence" is a good theme because according to (Stephen) Stigler's Law of Eponymy , "No scientific law is named after it's original discoverer." I believe that James Maxwell, while he was a genius, no doubt, left us with almost 20 Equations and that it was Oliver Heaviside who further transposed them into the 4 equations that now fit on so many t-shirts world wide. This video furthered my understanding about how transistors work for us. I love your stuff! Please keep it up!
Thank you for the clarification about the box which holds the electron being conceptualized as an infinite potential well--this is something that I've always wondered about and never saw explained before. At Minute 1:29, it's mentioned that the Heisenberg Uncertainty Principle creates the lack of knowledge of the position of the electron prior to measurement. The Heisenberg Uncertainty Principle tells us that to the extent we know the velocity, we can't find the position. But the main reason we can't pinpoint the position is that, prior to measurement, the electron is in a superposition of all positions in the box, per the Schrodinger Equation.
You are awesome . I am learning Quantum Physics in my Masters in Integrated Circuits and Systems here at IIT-Bombay in subject called Solid State Devices . While our professor did explain us for infinite potential well and the reason the electron cannot jump the barrier and be found on left or right 'top' sides of infinite potential well ( assuming infinite top is visible as is ) . Our professor then goes on to explain the E
Well wave cannot drop to 0 and stay there because solution to wave equation is always an exponential one and exponential solutions never stay at 0, they either exhibit exponential decay towards 0, or behave like a sine wave and wiggle around 0 if you allow complex exponents, but it still means that it has zeroes but doesn't stay 0 as y=0 is a line, which is linear and not exponential solution, and wave equation doesn't have a linear solution...
You should do an example problem for each of these videos. They are so great, but it would take it to the next level, to see actual quantum physics problems worked through that aren't just a theoretical proof type problems. Basically giving actual boundaries, Energy states, and probability values. Keep up the great work!
2:10 Who is the guy surfing on the wave function on a rainy day?? Because of quantum tunneling there is a limitation to how small transistors can get btw great video as always keep up the good work
darn, i really thought u were going to talk about the "why" of the decay instead of just the "what". oh, and i looked at that box and thought of wyoming.
The "what" explanation seems to be introducing overcomplicated sophistications into a comparatively simple "why" mechanism. The particle could be treated as a wave which must either reflect or refract at the barrier. There is a point, a very precise (uncertain and irreducibly random) point, where both possibilities exist and the particle/wave could go either way ... and it must go forward, it can only go one way, it can't go both ways ... so it then exists in one discrete state or the other without ever travelling "between" them. Sometimes this means the particle/wave (or some probabilistic fraction of many particles/waves) will "tunnel" to the other side of the barrier.
Hey Jade! I know you get a bajillion comments like this, but I've been meaing to to say for a while that i love your videos and that your channel is definitely one of my favorites. You do an exquisite job explaining complex subjects that I'd otherwise never understand. Thank you so much for doing what you do and keep up the good work!
Don't know the other two, but stars need it since the nuclei in the stars usually don't have enough energy to get close enough to fuse. So they basically need to tunnel the last bit
The DNA thing may be related with the fact protons can tunnel through enzymes; as for microscopy, fine-tuning of the potential barrier between an atom and the probe makes it so that when an electron tunnels through, it's read as a signal
ST microscopes have a very sharp needle that is brought to just above the surface of a material. Electrons can tunnel to the material from the needle causing a current. As the needle is scanned across the surface the magnitude of the current is kept constant by varying the distance between the needle and the surface. And that is how they know the shape of the surface.
Excluding the random extreme close-up, I genuinely think you are really starting to nail down the presentation in this videos. This chill and stripped down approach works really well, and btw, great video! ;)
I stumbled upon your channel looking for “how other people explain physics and math”. Glad I did! Love your energy and approach. However, note that in your tunneling problem, E is the same on the left and right of the barrier. It’s the amplitude that changes. This means that the “bumps” in your animation should be spaced equally on both sides, i.e., the wavelength is the same. Small detail. 😂 Keep making these videos! ❤ 9:02 You are brilliant - no pun intended! 😂
Earliest boi , also hi Jade this could be a little but different than your usual videos but could you do something on what do you do after graduating with a physics degree
@@additionaddict5524 go back to uni and study engineering. Nah but seriously I'm studying a dual degree of physics/engineering and on the physics side of things, naturally a big part of potential career prospects is working in academics. So, research/lecturing kinda stuff. Another option is teaching of some kind, high school physics/maths teaching is one. You could also try to get into industry as a statistician/data analyst/programmer/industry based physics researcher, even get into more economics/financial kinda stuff. You could also shift into more kinda engineering sides of things. But you'd most likely never be preferred over an actual engineering graduate (at least I wouldn't think so). So summarising, unless you work in academics, research or teaching, the jobs a physics degree will land, are mainly jobs that aren't completely physics based. This is just my experience in seeing graduates and might be different around the world
I like your explanation! But if it's an infinitely thick-walled box, can it have an "outside" to begin with? I think the probability of it outside being zero is because there is no outside.
Years ago now, in our Quantum Mechanics Lab we did the tunneling experiment by reflecting a microwave beam within salt blocks ( more commonly used as nutritional supplements for cattle). We "shined" the microwave beam into a right angled rectangular prism and the evanescent wave would jump (tunnel ) the gap to an identical salt prism almost touching (gaped) at the hypotenuse. Thanks for doing Your videos.
No one is ever going to be as cool as the stick man surfing the EM wave! Great way of explaining the concepts while presenting it in a clear yet humourous way!!
What the?That's the best video so far on tunneling on youtube.Sorry for not subscribing and looking into your channel before.Nice job.Keep it up and never lose that smile and energy😊
To answer your question about frustrated internal reflection, I think if you consider the barrier of potential as consisting of many vibrating waves, there is a some chance that some of those vibrations will constructively interfere with the wave of light, pushing it just slightly passed the barrier itself, and producing the evanescent wave. In other words, throwing a tennis ball at a vibrating wall, if that wall has just the right vibration, it could facilitate the tunneling of that tennis ball just barely through its own medium. (Please feel free to correct me if this doesn’t make sense, just a hypothesis).
I come from Tom Scott's channel. That video on knotss was HECKING AWESOME. It blew my mind! I can't wait to watch your videos on Quantumn, I'm actually in Quantumn 2 in my college course but sure a refresher is always nice!
I was playing around on the iPad checking on my settings and I ended up asking Siri random questions I was curious to her responses! So I asked her question that I knew something about which was “can you explain to me what quantum tunneling is“ and she listed three options your video was the second option! I practically subscribed immediately and then went to the about section on your page, to see if you had a Twitter account therefore I followed it as well! Not that this matters but generally it’s a channel I really enjoy “educational wise“ I’ll pretty much instantly follow them on Twitter as well“
Not to mention, I was in flight/aviation in high school, and I was an NROTC nerd! Ironically enough I never took physics or chemistry! But what channel is like yours which “I’m glad I found“ I honestly learned more about physics chemistry etc. primarily physics and quantum mechanics/Quantum physics! Do to videos like yours and so far yours is one of the best that explains also you label your videos and don’t deviate away from the topic! I feel like anybody that watches your videos can easily understand what you’re explaining!
Great video. At 5:47 you request a good physical explanation why the wave cant change direction at an interface without an evanescent wave. My take of this is: The wave has to "decide" what to do when meeting an interface. In order to make this decision it must know what kind of interface it is, so it has to probe it before it can "decide" what to do next. Probing means it must penetrate the material to some degree in order to interact with the medium. For this it need the evanescent part.
To sort of answer your question, why it can't abruptly go to zero, it's because of the relative permittivity. As epsilon is a finite (complex) number, the exponent is small but non-zero. AFAIR, the imaginary part is responsible for the attenuation. So for it to go to zero, the imaginary part has to be very large (like in metals). I hope this sets you off in the right direction to study more (I don't remember the details, sorry). PS: the wavefunction is not the probability: prob. = psi*psiconjugate. So that description of probability "oscillating" isn't accurate ;). Good video :)
I wish these videos were around when I was really into this in high school. I still am but now I’m in university and this was helpful toward my learning
The best summary my teacher ever gave me of the Quantum realm was that it is nonsense. The truly and truly fast realm of subatomics do not behave as they would in the wider world. Fascinating lesson Keep up the good work!
I’m sorry that I can’t do your level of math with my learning disability’s but I have a thirst for knowledge that can’t be quenched . So I thank you for understanding the catch phrases.😕
Hey Jade. Regarding the intuition of the evanescent wave issue you mentioned in the video, I think that appears because the reflection boundary is not hard enough. If you have a very high potential barrier (like infinite well), then you wont have the evanescent wave. Intuitively, imagine a wave travelling to a fixed point, if you pin this fixed point very hardly, then no evanescent wave will appear. But if you dont pinch that hard, let it to move a little bit (a softer boundary), then the wave might propagate a little bit.
For the glass example, Since the transmission of energy is never 100 % therefore a very small amount of the energy absorbed by the boundaries edge atoms continues into the evanescent wave due to remittance from the elections dropping orbitals but too close to the edge to reflect? Like the exponential e^-x approachs infinity but never gets there.
amazing video! I think the evanescent wave could occur just because entropy must maximize by doing so and/or when calculating the path of least action (stationary action) of the light by deriving the Lagrangian. I think it happens this way in particular because no transfer of anything in nature (energy, information, mass, etc) is perfect, so I would expect some imperfection in that angle of perfect reflection as well (maybe also be uncertainty principle and that causes the imperfection and subsequent evanescent wave?). I have no idea but very fun and cool to speculate about
For that side question "why can't a wave just abruptly end?" I think of this in terms of frequencies or momentum. If you take the Fourier transform of a wave that suddenly stops at a wall, the frequency spectrum is infinitely wide. Like for the particle in an infinite box, the wavefunction is continuous but not differentiable at the walls, which gives the momentum spectrum oscillations out to very high frequencies. With any real-world finite potential, the evanescent wave can make the momentum spectrum, or the spatial frequency spectrum, better contained and not oscillate out to infinity. Or another way to say it - you don't have enough energy to abruptly stop. The evanescent wave is a lower kinetic energy solution than a hard stop.
I swear I fell in love with this girl for the way she communicated the Abstruse and vague idea of quantum mechanics in such a lucidity, I actually give an accolade and appraisal to myself as well because I got fascinated to her.😅
5:19 You have to think about the waves as oscillations of the electric and magnetic fields. Since there is oscillation at the boundary, the fields must be affected in the immediate vicinity. The best analogy I can think of now, for some reason, is contagious dancing in a crowd. The people on the other side of the 'boundary' don't really want to dance, since the people on this side are directing all the 'energy' of their dancing only to the people on the same side, but those on the other side who are nearby can't help but sway a little.
Back in the sixties I enlisted in the Marines, because of my high school education I ended up in the advanced electronics school. While there I was introduced to quantum tunneling in solid state electronics. We got hit with tons of physics and math but most worked together and got through it.
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The humility you bring to these videos where you're willing to ask for explanations and admit what isn't your forte is really inspiring and makes some pretty esoteric stuff a lot more approachable.
Hear hear! :) I never heard of evanescent waves before, so I am very curious for the explanation as well (none in the comments so far :-/...).
I can't say I understand this enough to explain it, but 3blue1brown has an excellent video correlating quantum tunneling (via the Uncertainty Principle / Unsharpness Relation) to a Fourier analysis. Whether true or not, it helps me make sense of that and the "infinite sharpness" required to make waves simply start, end, or turn 90 degrees without side effects. I believe this is also made more explicit in another video I can't readily find. th-cam.com/video/MBnnXbOM5S4/w-d-xo.html
@brian' It would be fun if just once she was flippant and punctuated every explanation with "Duh!" 😂
First of she can’t even explain the quantum mechanical humility copanhageng interpreters have
You bring quantum mech.. to a whole new poetic level
“Unlike a ball, we can’t pinpoint exactly where an electron is.”
Wow, balls must be really good at physics to be able to pinpoint exactly where an electron is.
XD made my day!
Balls have Heisenberg compensators.
Nothing But The Austin These balls break the laws of quantum mechanics. Wait, that sounds wrong...
what kind of balls? balls of steel?
Ah, the old quantum-a-roo
Cats are inherently non-classical objects [1]. My cat can move through a closed cat door, but he never does so when I'm there observing him (he just meows for me to open the cat door). Is it possible that he has harnessed quantum tunneling?
[1] Schrödinger, 1935
Lmao
Im dying
xD
The tunneling is his wife wanting the cat to stop whining.
Lol
Cats are gods, they can manipulate the laws of physics
The Egyptians were right
I think quantum field theory might help with intuition. Instead of thinking in terms of particle vs wave you can view everything as disturbances in fields. This means that particle behavior arises from interacting perturbations in fields and the interactions of different “particles” or a complicated multiple perturbation event can create a field effect without the particle seeming to cross that distance.
Really the move from thinking of particles and waves to considering fields was a huge moment for me!
Yeah, but it leads to similar catastrophes as treating light like a wave... Then you gotta come up with new corrections...
You put water into a teapot, it becomes the teapot.
Now water can flow or it can crash.
Be water, my friend."
That electron doesn't look very happy.
Oh well, he's just being negative.
YoungTheFish so does a positron see the potential well as half full, then?
John Shioli its an 'infinite' potential well, there is no "half full"
@Anzu Shiina Perhaps, but some infinities are bigger than others.There is an infinite quantity of whole numbers. There are half as many odd numbers, though there is an infinite quantity... th-cam.com/video/elvOZm0d4H0/w-d-xo.html
Edit: series=quantity
@@Pekkhum Well, technically there are not infinities bigger in quantity, but there infinities of superior order (which contain numbers that other infinities does not).
@@martiddy Much more accurate. 🙂
3:45 that got intense real quick
Pleased to meet you. Welcome to the Tom Scott Effect!
Im here from tom scott........
I too tunnelled here from Tom Scott
I am from Scott as well
lol.
Hey thee
Video: evanscent
My brain:
wake me up! wake me up inside!
And I love how the definition of evanescent literally just describes the band. Lol
Omg I was not the only one then! nice haha
CAN'T WAKE UP !!!!!!!
thank you!!!
Saaaave meeeeehhh!
So, there's a miniscule probability that some Quantum Mechanics concepts will tunnel into my ape brain? Too bad they are evanescent :(
I can't wake up
@@eaterdrinker000 WAKE ME UP INSIDE
Now I'm having flashbacks to being drunk at raucous bars in 2003.
Somebody save me and wake me up because I can't wake up, save me
get closer to the computer
Just here to watch the video and see if this channel is at a million subs yet. No...alright will check back next week.
omg majorprep, your comment actually made me to check if your channel is millions sub yet, hahah. Great job both of you
Still only a quarter million...
Been a year bruv
Yes! This channel deserves a million
Looks like you're going to be checking back for a long time yet.
I think I suffer from 'frustrated total internal reflection'...
Ditto. Maybe a change to our boundary might help with some refraction
Me trying to meditate...
"frustrated total internal rejection"
I've often heard that quantum tunneling 'sometimes happens' when the energy potentials make it possible, but not about the evanescent wave function. I'm very glad to have learned something today. Thank you so much for taking it a couple steps beyond what is so often repeated, while keeping the math accessible to non-physicists.
Great! Here is a recent experiment with an interpretation:
th-cam.com/video/w0fuxjhuD9g/w-d-xo.html
I love your honesty and references to previous videos, it shows you analyse past experiences, take on board feedback and aim to create a more efficient future with more understanding examples 😊
Thank you for this. I've never encountered a description of quantum tunneling that made the remotest bit of sense to me. This gave me what I can comfortably say is a vague understanding, which, considering it's quantum physics, is high praise :)
This is the best hidden gem of a channel I've ever found:)
It was harder for me to pretend the pencil was a straw then understand Quantum Tunneling
fortunately I don't have that problem since I just assume they are both cylinders with zero radius and infinite length. The perks of being a physicist...
@@solsystem1342 that straw with zero radius would make drinking really suck....XD
I also presume it was harder to understand basic English grammar???
@@solsystem1342" cylinder with zero radius and infinite length". Wouldn't that just be a line?
@@achyuththouta6957 Seriously though for a moment, not necessarily. It could also approximate a cylinder with a very small radius and large height in some situations. Such as trying to find the electric field inside a cavity.
I may know why that drop of light occurs. Like when we throw a ball on floor it reflects. In this process it losses very little kinetic energy to floor . Thats why we feel vibration in floor during the process.
Now imagine ball as a wave of force. This wave will reflect like a ball at a certain angle but very little wave will pass through floor.
Now this may what is happening with light. When it reflects some of its energy or em wave passes through the surface . And thats why we may see a drop of light...
You beat me by 2 years
Tunneling is also a term in game/physics engines which describes when collisions are missed because the simulated objects are too small and too fast. It's a result of simulating things in discrete timesteps (two objects might only be colliding for half a timestep), and I think it's named after quantum tunneling.
True..
The e^(-x) function approaches but never reaches zero. Does this mean that quantum tunneling is always possible, but just increasingly improbable, for any non-infinite potential barrier?
First, does QM applies to non-subatomic particles as well, like people?
Second, does that mean there is a non-zero, though perhaps 10e-100, that I am actually at you house, which sounding from you name may be in Erupoe, er Europe?
I suppose that if one is made of 10^25 particles or thereabouts then there is a reasonable chance that a handful of their particles have tunneled away from what one considers their body, for certain definitions of "reasonable". But the remainder will be at about where they are expected to be.
I used to have a sign on my bedroom door that read, "This may be that one in a trillion chance that the atoms of your body align perfectly with those of this door, and you can walk right through it. Go ahead. Try it."
Yep you got it bud
@@stellarfirefly lol, the more they try, the more chances they'll find their tooth beyond that door😆
Yup!!!! It could, in theory, tunnel in an amazingly great distance, just be extremely unlikely to do so. E.g. if the barrier is 1 m thick, and the tunnel constant is about one per nanometre (just as a very rough for atomic scale), then since 1 m = 10^9 nm, you get tunnel probability on the order of e^(-10^9) ~ one shot in 10^434,294,481 - a number that is so large, at over 434 million digits - that simply writing down its _digits_ would fill many volumes, to find it tunneled in by that highly-macroscopic distance. That's _hundreds of millions_ of _orders of magnitude_ less likely than winning the lottery jackpot every single drawing for the rest of your entire life _and_ getting hit by a bolt of lightning every day _and_ surviving each and every strike _and_ randomly encountering every single last famous person on the planet every day _and_ going to beers with each and every one, all in the same lifetime.
Indeed, it is so fantastically unlikely that we could say with extreme confidence - enough to bet all the money on the entire planet and it'd be a _very_ safe bet with no foolishness whatsoever - that an event of this probability has _never occurred once in the entire history of the known parts of the universe_ .
Jade, you asked for an explanation to evanescent wave decay. A good example is to look at ocean waves. Near the surface a measurement of the hydrostatic pressure varies in proportion to the varying wave height above the point of measurement. As the point of measurement goes deeper that point is no longer merely affected by the wave directly above it but by the combined effect of waves to either side of vertical. Assuming the waves are sinusoidal the average effect upon the variation of hydrostatic pressure tends to diminish as the contribution of multiple peaks will tend to cancel the contribution of multiple troughs. There is also a diminishing effect as you get farther from the wave due to depth (I suspect proportional to 1/r where r is the distance to the wave). There is a formula which describes the variation in hydrostatic pressure due to the waves as a function of depth, and lo and behold just as in the case of the evanascent wave that variation decays exponentialy. I am a retired sonar engineer, and this problem came up in the course of my work.
You are so good at explaining sophisticated subjects...like your videos so much 👍👍👍
Hi Jade. You alluded the continuity of evanescent waves at around 5:49. Fundamentally in nature, there are really no abrupt changes at things with boundaries--it's exactly what you are explaining when you described non-infinite potential wells. You have to have a matched boundary condition and the natural way that happens with optical materials is to have an exponential fall off. I think you can look at it as a photon having a physical extent in that is has a spatial wavefunction associated with its position. As the photon approaches the boundary in the glass, the wave function of its position crosses the boundary and extends outside the boundary. The shorter the wavelength of the photon, the more confined it's likely position is and the faster the evanescence wave (field) strength falls off on the other side of the boundary--the wave number gets larger with photon energy causing the field to fall off faster. Thanks for making videos on this stuff.
Actually, there are no laws that forbids discontinuity, and they do occur in nature, for EM wave propagation in particular, even though E and H are continuous across boundaries, D and B can be discontinuous. Discontinuity is particularly prominent in phase transition and quantum mechanical phenomena like the photo-electric effect and laser pumping, where there's a threshold on the input parameters which triggers a different behaviour once it is crossed.
I'm not a physicist but a mathematician, so I'm curious about this. How can B possibly be discontinuous if you need to be able to take its gradient, curl and time derivative in order to even formulate Maxwell's equations?
Time derivative isn't really a problem since the discontinuity is only spatial. For the gradient, well, the component of B perpendicular to the surface actually has to be continuous, while the parallel component doesn't have to be, okay, so you might still not be able to take the gradient, but we're physicists, and we're allowed to just switch to the integral form when we want, and you can take the limit as the surface of the integral approaches 0 if you want to be all rigorous. For the curl, well, Maxwell's equation is written in terms of the curl of H rather than B actually (except for non-magnetic material where B = H) so it's fine there as well. Although, formally we consider the perpendicular and parallel components separately and take the limits as the line integral shrink rather than explicitly taking the derivative at the boundary.
If you don't like the whole limit thing, you could of course fiddle around with weird functions like the Dirac delta which is obviously discontinuous but is defined to have an integral and derivative. But that's a bit much for a youtube comment and a bit out of my comfort zone tbh.
I guess I have to correct myself, I misremembered before but technically all of E,D,B,H can all be discontinuous. However, Maxwell's equations do force certain components to be continuous across the boundary.
Cool, thank you for taking the time to type out such a detailed answer. I was suspecting that it would be something along the lines of switching to integral form or working with distributions, which don't have to be functions at all (such as the Dirac delta). Maybe at some point, I'll find the time to delve deeper into physics and will then remember your comment ;)
@Phanbichdanosaurmythicalbeast etc. etc. epic memes are appreciated by all
I am a 1st year engineering student and I missed the lecture on wave function.
But YOU came to my rescue and helped me in that .
VERY VERY THANK YOU .
🎈🎉🎈🎉
Because of the Wave function , quantum mecanichs is stuck for 100 years....Now people see the need more and more to just get rid of the wave function , like the ones that are interested in quantum gravity , or quantum information..... For me wave function is something that DOES work for things that are emergent.....when you go deeper, something else must replace the wave function..
Its the same like F=ma work... but for relativity not.....
Everthing is emergent if you loock hard enough and every emergent thing has his own "wave function " --meaning the thing that describe the best....for the electron its the wave function....for the apple , planets , its F=ma...
The next step after the wave function I believe that its information....
@@cazymike87 ? What pls explain ?
What wave function its for physycs now is what Newton gravitys was for Einstein back then.....something old, ineficent , that cant explain the whole picture....
There are many scientists that loock into this .... Try to search for your own on this matter.
The wave function its not how Universe works !
If you search quanrum computer then you will notice that the whole ideea its to just bypass the colapse of the wave function using something deeper : information.
Outhers try to baypass the wave function using mathematical shapes ....
There are many approaches for this subject.
But its something that everyone knows by now : Wave function it is not fundamental.
@@cazymike87 what are you talking about? Name me a reputable physicist who is suggesting to get rid of the wavefunction. If you get rid of the wavefunction you completely throw out all of quantum mechanics. Moreover, quantum computing's foundation is the wavefunction and entanglement of quantum states.
I love your videos.
That's it. That's all I have to say. I can't think of any compliments that do this video justice.
I liked the surprise goodbye at the end made me jump! I’m hanging thru every word you say so that one was an unexpected surprise, fun
!!!
You gave me an "ah-ha!" moment of my own!
A few months ago I was researching equations of state, specifically SAFT. It basically models the molecular interactions between particles. I came across certain potentials and what not and it all made enough sense for me to at least conclude that the potentials affect the strength of interactions. Fast forward to today and here you are explaining what a potential well is and I'm like "OH MY GOD! THATS IT! THATS THE THING!!!!"
You do amazing work. Keep it up and thank so much for that wonderful moment!
Some of questions. 1) does the energy of the particle in the wave function determine how long the evanescent wave will last?
2) If the energy of the particle does contribute to the duration of the evanescent wave, is there an upper limit to how long the evanescent wave can exist?
3) does the material that the evanescent wave travels thru effect the duration of the wave? for example can an electron tunnel thru 1mm of paper, but it couldn't make it thru 1mm of lead. (a millimeter is a huge distance for an electron, so assume I am smart enough to know the correct units of measurement )
4) does the mass of the particle in the wave effect the length of the evanescent wave? Would a photon evanescent longer than an electron (all other things being equal)?
1) & 2) This is the time- _independent_ problem - so no relevant notion of "lasting" here
3) Yes; in QM lango, we'd model the lead wall as a _higher_ barrier than that associated with the paper
4) Yes; the wavelength is inversely proportional to the (square root of) mass (but notice that, although related to the exponential decay term in the barrier, in that region that term is not actually a wavenumber k (k = 2*pi/wavelength) )
I have a more complete answer to 1 and 2. The wave function inside of the barrier is exponentially decaying. And this decay is directly proportional to the energy. The more energy the particle has, the greater probability it has to tunnel through the barrier. Of course, this is only for the case when the particles energy is less than that of the barrier. If this condition fails, then tunneling doesnt occur because the particle is free to easily overcome the barrier energy. Then the wavefunction is oscillating, not decaying. But this is unrelated to the time. If youre thinking at this high of a level, I challenge you to just look at the solutions. You should be able to understand it
the wave doesn't stop at any distance just like how the function e^(-x) approaches 0 but never quite reaches it. So a electron could travel through 10 km of solid rock it just has such a tiny chance it probably will not happen before the heat death of the universe
Finally, an explanation of an effect I have to know most of my life but whose maths is too complex for my small brain to work out. Thank you.
A good way to Intuit quantum tunneling (for me anyway) is to imagine a wave (of water) breaking on rocks. Some of the water jumps the rocks and ends up on the other side. Wave mechanics is (for me) very intuitive if you visualize the waveform as a literal wave made of a fluid (the water analogy also works for GR and the warping of spacetime if you include bubbles in your visualization). Hope this helps in some way
That's just details
@Razvan J the indivisible particle (quanta) IS the wave, so of course it passes through entirely, that's the meaning of the word "indivisible"
Also the details are in the mathematics. This is about a way of picturing the mathematical results in your head.
Still gotta actually DO the maths
@Razvan J that's your opinion and you're welcome to it. I shared the mental imagery that I personally use to make sense of the mathematics. If it doesn't work for you, then you're more than welcome to come up with your own mental imagery. However once you've done the maths a few thousand times the picture you have in your mind doesn't really matter anymore because it'll be replaced by the mathematical model and you'll gain a natural (mathematic) intuition for it.
@Razvan J the wavefunction of an electron occurs in something called a Hilbert space. The modulus of the wavefunction squared gives you the probability density of the particle's physical location. Sometimes that probability distribution extends beyond the initial boundary conditions which are imposed on the equation, and therefore the probability that the electron will be found outside the boundary is non-zero.
Using a macroscopic wave is the method by which my brain naturally puts all that information into a picture.
That's all.
Like I said the details are in the mathematics, and without the mathematics the entirety of quantum mechanics means exactly nothing.
@Razvan J from textbooks and lectures, and I didn't HAVE to learn quantum mechanics, I chose to.
The reason you have to do the maths a bunch of times is because it's the language of QM. Much like how you can't read a book until you have gone through the alphabet a bunch of times and know what all the letters are.
I love how enthusiastic you are explaining all this stuff to us 😊
Jade these continue to be wonderful to watch. Clearly lots of people agree with me, which is reassuring. "Evanescence" is a good theme because according to (Stephen) Stigler's Law of Eponymy , "No scientific law is named after it's original discoverer." I believe that James Maxwell, while he was a genius, no doubt, left us with almost 20 Equations and that it was Oliver Heaviside who further transposed them into the 4 equations that now fit on so many t-shirts world wide. This video furthered my understanding about how transistors work for us.
I love your stuff! Please keep it up!
Thank you for the clarification about the box which holds the electron being conceptualized as an infinite potential well--this is something that I've always wondered about and never saw explained before. At Minute 1:29, it's mentioned that the Heisenberg Uncertainty Principle creates the lack of knowledge of the position of the electron prior to measurement. The Heisenberg Uncertainty Principle tells us that to the extent we know the velocity, we can't find the position. But the main reason we can't pinpoint the position is that, prior to measurement, the electron is in a superposition of all positions in the box, per the Schrodinger Equation.
Outer Wilds brought me here
Didn't expect to see you here. Love your videos btw
Never thought you liked this stuff too, nice!
Outer wilds is one of THE best games in the history of ever
I have been working on flash storage for the past 10 years and all of your solid state drives actually use quantum tunneling to store the bits!
“Isn’t that interesting?!” And I don’t even know what I’m looking at lol
It wasn't until she circled the red trail that I realised I wasn't meant to be looking at the equation :D
Only way to solve that is to take a course at Uni.
Lovely video. I have just started to work on Quantum Biological Electron Transfer and your video helped me to get some basics rights.
Amazing vid!! Didn’t feel like a dumb ass the whole time, your kind vibe really puts me at ease and heck the content is cool. Nice one
still cant believe how well you explained everything
Best explanation I've seen so far, after 6 vids
You are awesome . I am learning Quantum Physics in my Masters in Integrated Circuits and Systems here at IIT-Bombay in subject called Solid State Devices . While our professor did explain us for infinite potential well and the reason the electron cannot jump the barrier and be found on left or right 'top' sides of infinite potential well ( assuming infinite top is visible as is ) .
Our professor then goes on to explain the E
At 3:30 I have a feeling there's a typo in the last of Maxwell's equations, Ampere's Law should be curl not divergence!
I swear, your method of explaining along with your visuals make quantum mechanics so much easier to comprehend.
8:27 'I didn't really understand the schrodinger's equasion untill I solved it myself'
YOU DID WHAT?
It is solvable in easy cases, but even then it is quite hard
I love the general background music on your videos. It's oddly relaxing.
Well wave cannot drop to 0 and stay there because solution to wave equation is always an exponential one and exponential solutions never stay at 0, they either exhibit exponential decay towards 0, or behave like a sine wave and wiggle around 0 if you allow complex exponents, but it still means that it has zeroes but doesn't stay 0 as y=0 is a line, which is linear and not exponential solution, and wave equation doesn't have a linear solution...
You should do an example problem for each of these videos. They are so great, but it would take it to the next level, to see actual quantum physics problems worked through that aren't just a theoretical proof type problems. Basically giving actual boundaries, Energy states, and probability values. Keep up the great work!
2:10 Who is the guy surfing on the wave function on a rainy day?? Because of quantum tunneling there is a limitation to how small transistors can get btw great video as always keep up the good work
ah correction, there is a limit to how small they can get and still be decently reliable
Your passion for the subject is commendable. Thanks for making me pass this semester :)
"Can you learn quantum mechanics without math?"
" *B R I L L I A N T D O T O R G* "
Great video.
The explanation of quantum tunneling is like reducing a fraction to its lowest terms.
Wonderfully simple but yet elegant !!!
😺😺😺
darn, i really thought u were going to talk about the "why" of the decay instead of just the "what". oh, and i looked at that box and thought of wyoming.
The "what" explanation seems to be introducing overcomplicated sophistications into a comparatively simple "why" mechanism.
The particle could be treated as a wave which must either reflect or refract at the barrier. There is a point, a very precise (uncertain and irreducibly random) point, where both possibilities exist and the particle/wave could go either way ... and it must go forward, it can only go one way, it can't go both ways ... so it then exists in one discrete state or the other without ever travelling "between" them. Sometimes this means the particle/wave (or some probabilistic fraction of many particles/waves) will "tunnel" to the other side of the barrier.
Now this i call a good explanation ! I like that you included the equation into the video. It would be cool if you could do that with more videos.
Could quantum tunnelling be explained by errors in the simulated universe's collision detection?
wow, i never thought of it that way. would love to know the answer.
No, and we’ll now have to scrub you. Thanks for the extra work.
Hey Jade! I know you get a bajillion comments like this, but I've been meaing to to say for a while that i love your videos and that your channel is definitely one of my favorites. You do an exquisite job explaining complex subjects that I'd otherwise never understand. Thank you so much for doing what you do and keep up the good work!
Why is quantum tunneling essential to nuclear fusion in stars, spontaneous mutation in dna and scanning tunnel microscopy?
Don't know the other two, but stars need it since the nuclei in the stars usually don't have enough energy to get close enough to fuse. So they basically need to tunnel the last bit
The DNA thing may be related with the fact protons can tunnel through enzymes; as for microscopy, fine-tuning of the potential barrier between an atom and the probe makes it so that when an electron tunnels through, it's read as a signal
ST microscopes have a very sharp needle that is brought to just above the surface of a material. Electrons can tunnel to the material from the needle causing a current. As the needle is scanned across the surface the magnitude of the current is kept constant by varying the distance between the needle and the surface. And that is how they know the shape of the surface.
Excluding the random extreme close-up, I genuinely think you are really starting to nail down the presentation in this videos. This chill and stripped down approach works really well, and btw, great video! ;)
Brain.exe is not responding
I stumbled upon your channel looking for “how other people explain physics and math”. Glad I did! Love your energy and approach. However, note that in your tunneling problem, E is the same on the left and right of the barrier. It’s the amplitude that changes. This means that the “bumps” in your animation should be spaced equally on both sides, i.e., the wavelength is the same. Small detail. 😂 Keep making these videos! ❤ 9:02 You are brilliant - no pun intended! 😂
Earliest boi , also hi Jade this could be a little but different than your usual videos but could you do something on what do you do after graduating with a physics degree
go in a hole and cry because you're never going to use it
@@additionaddict5524 go back to uni and study engineering. Nah but seriously I'm studying a dual degree of physics/engineering and on the physics side of things, naturally a big part of potential career prospects is working in academics. So, research/lecturing kinda stuff. Another option is teaching of some kind, high school physics/maths teaching is one. You could also try to get into industry as a statistician/data analyst/programmer/industry based physics researcher, even get into more economics/financial kinda stuff. You could also shift into more kinda engineering sides of things. But you'd most likely never be preferred over an actual engineering graduate (at least I wouldn't think so). So summarising, unless you work in academics, research or teaching, the jobs a physics degree will land, are mainly jobs that aren't completely physics based. This is just my experience in seeing graduates and might be different around the world
This was by a mile or ten the best science communication video on quantum tunelling I've ever seen.
I like your explanation!
But if it's an infinitely thick-walled box, can it have an "outside" to begin with?
I think the probability of it outside being zero is because there is no outside.
watched alot of videos on TH-cam and this is the first one that explained in a way I could understand. Good work!
Quantum jumping with J A D E 👩🏫👸👊👋👏👍👌
Years ago now, in our Quantum Mechanics Lab we did the tunneling experiment by reflecting a microwave beam within salt blocks ( more commonly used as nutritional supplements for cattle). We "shined" the microwave beam into a right angled rectangular prism and the evanescent wave would jump (tunnel ) the gap to an identical salt prism almost touching (gaped) at the hypotenuse. Thanks for doing Your videos.
Exponential decay never reaches 0 though.
Jonathan Dirks as x approaches negative infinity it does.
@@dezznutts1197 "approaches"
Attila do you actually understand what that means
@@dezznutts1197 I think so
Attila I recommend to search it up. It’s called “limits”. It’s weird.
Really liked the video, the frustrated total internal reflection part really helped me with visualizing what is going on.
Thumbed up for shamelessly admitting that you're not good at physical experiments. Neither am I. :(
Quantum tunnelling: exists The Higgs field: cowabunga
Hands up if Tom brought you here?:-)
4:30 I think the term Evanescent wave is apt because, after a brief moment, the light ends up waking up inside the stuff it's passing through.
No one is ever going to be as cool as the stick man surfing the EM wave!
Great way of explaining the concepts while presenting it in a clear yet humourous way!!
What the?That's the best video so far on tunneling on youtube.Sorry for not subscribing and looking into your channel before.Nice job.Keep it up and never lose that smile and energy😊
To answer your question about frustrated internal reflection, I think if you consider the barrier of potential as consisting of many vibrating waves, there is a some chance that some of those vibrations will constructively interfere with the wave of light, pushing it just slightly passed the barrier itself, and producing the evanescent wave. In other words, throwing a tennis ball at a vibrating wall, if that wall has just the right vibration, it could facilitate the tunneling of that tennis ball just barely through its own medium. (Please feel free to correct me if this doesn’t make sense, just a hypothesis).
I come from Tom Scott's channel. That video on knotss was HECKING AWESOME. It blew my mind! I can't wait to watch your videos on Quantumn, I'm actually in Quantumn 2 in my college course but sure a refresher is always nice!
First explanation of quantum tunnelling that makes sense. Thanks ! KeepSmiling 😊🌺
It's very great quantum tunneling!!! I really am eager to see some videos on highs boson..
I was playing around on the iPad checking on my settings and I ended up asking Siri random questions I was curious to her responses! So I asked her question that I knew something about which was “can you explain to me what quantum tunneling is“ and she listed three options your video was the second option! I practically subscribed immediately and then went to the about section on your page, to see if you had a Twitter account therefore I followed it as well! Not that this matters but generally it’s a channel I really enjoy “educational wise“ I’ll pretty much instantly follow them on Twitter as well“
Not to mention, I was in flight/aviation in high school, and I was an NROTC nerd! Ironically enough I never took physics or chemistry! But what channel is like yours which “I’m glad I found“ I honestly learned more about physics chemistry etc. primarily physics and quantum mechanics/Quantum physics! Do to videos like yours and so far yours is one of the best that explains also you label your videos and don’t deviate away from the topic! I feel like anybody that watches your videos can easily understand what you’re explaining!
Great video. At 5:47 you request a good physical explanation why the wave cant change direction at an interface without an evanescent wave. My take of this is:
The wave has to "decide" what to do when meeting an interface. In order to make this decision it must know what kind of interface it is, so it has to probe it before it can "decide" what to do next. Probing means it must penetrate the material to some degree in order to interact with the medium.
For this it need the evanescent part.
9:44 actually startled me, lol.
To sort of answer your question, why it can't abruptly go to zero, it's because of the relative permittivity. As epsilon is a finite (complex) number, the exponent is small but non-zero. AFAIR, the imaginary part is responsible for the attenuation. So for it to go to zero, the imaginary part has to be very large (like in metals). I hope this sets you off in the right direction to study more (I don't remember the details, sorry).
PS: the wavefunction is not the probability: prob. = psi*psiconjugate. So that description of probability "oscillating" isn't accurate ;).
Good video :)
I have a physics degree and I swear I never learned about this evanescent wave phenomenon upon total internal reflection. Very cool and interesting.
Barrier: "You shall not pass!"
Electron: "Hehehe"
I wish these videos were around when I was really into this in high school. I still am but now I’m in university and this was helpful toward my learning
The best summary my teacher ever gave me of the Quantum realm was that it is nonsense.
The truly and truly fast realm of subatomics do not behave as they would in the wider world.
Fascinating lesson
Keep up the good work!
This was the most amazing explanation I've seen so far
I work in optoelectronics for telecommunications. Very good video, especially the total internal reflection and exponential decay.
I’m sorry that I can’t do your level of math with my learning disability’s but I have a thirst for knowledge that can’t be quenched . So I thank you for understanding the catch phrases.😕
Hey Jade. Regarding the intuition of the evanescent wave issue you mentioned in the video, I think that appears because the reflection boundary is not hard enough. If you have a very high potential barrier (like infinite well), then you wont have the evanescent wave. Intuitively, imagine a wave travelling to a fixed point, if you pin this fixed point very hardly, then no evanescent wave will appear. But if you dont pinch that hard, let it to move a little bit (a softer boundary), then the wave might propagate a little bit.
For the glass example, Since the transmission of energy is never 100 % therefore a very small amount of the energy absorbed by the boundaries edge atoms continues into the evanescent wave due to remittance from the elections dropping orbitals but too close to the edge to reflect? Like the exponential e^-x approachs infinity but never gets there.
Wait what? 😕 What does that mean?
You made this really fun to learn. Thanks for keeping your audience in mind
amazing video! I think the evanescent wave could occur just because entropy must maximize by doing so and/or when calculating the path of least action (stationary action) of the light by deriving the Lagrangian. I think it happens this way in particular because no transfer of anything in nature (energy, information, mass, etc) is perfect, so I would expect some imperfection in that angle of perfect reflection as well (maybe also be uncertainty principle and that causes the imperfection and subsequent evanescent wave?). I have no idea but very fun and cool to speculate about
For that side question "why can't a wave just abruptly end?" I think of this in terms of frequencies or momentum. If you take the Fourier transform of a wave that suddenly stops at a wall, the frequency spectrum is infinitely wide. Like for the particle in an infinite box, the wavefunction is continuous but not differentiable at the walls, which gives the momentum spectrum oscillations out to very high frequencies. With any real-world finite potential, the evanescent wave can make the momentum spectrum, or the spatial frequency spectrum, better contained and not oscillate out to infinity. Or another way to say it - you don't have enough energy to abruptly stop. The evanescent wave is a lower kinetic energy solution than a hard stop.
I swear I fell in love with this girl for the way she communicated the Abstruse and vague idea of quantum mechanics in such a lucidity, I actually give an accolade and appraisal to myself as well because I got fascinated to her.😅
THIS IS THE BEST EXPLANATION EVERRRRRRRRR SOOOO INTUITIVE
Extremely helpful
Please keep bringing stuff like this
It's Really easy to understand the concepts from u....
Thank u
This instalment proved even more useful than I had expected.
Yaya keep talking , I love how you explain these complicated concepts so easily🤓🔥
5:19 You have to think about the waves as oscillations of the electric and magnetic fields. Since there is oscillation at the boundary, the fields must be affected in the immediate vicinity. The best analogy I can think of now, for some reason, is contagious dancing in a crowd. The people on the other side of the 'boundary' don't really want to dance, since the people on this side are directing all the 'energy' of their dancing only to the people on the same side, but those on the other side who are nearby can't help but sway a little.
This video is so good! Was looking to understand quantum tunneling in the isotope effect and this helped alot!
Back in the sixties I enlisted in the Marines, because of my high school education I ended up in the advanced electronics school. While there I was introduced to quantum tunneling in solid state electronics. We got hit with tons of physics and math but most worked together and got through it.