How to Make a Quantum Tunnel In Real Life

okay everyone today I'm going to be showing you real-life quantum tunneling and I'll also be explaining how you can do it for yourself at home so first let me explain what quantum tunneling even means so before quantum mechanics came around all we had was classical physics and classical physics goes something like this if you know at time 1 the position and velocity of this ball then you can easily predict at time 2 the position and velocity of that ball so it's easy to predict if you have a ball flying through the air where it's going to be later and it turns out that classical mechanics works really well for large objects but when you get things that are really small it turns out that they don't work so well let's say for example this were now the size of an electron if that were the case we can no longer predict at some future time where exactly the ball is going to be but we have to give some probability curve of where it's most likely to be when we measure it and as a result of this some weird things can happen and one of them is called quantum tunneling now quantum tunneling goes like this let's say for example there's some barrier that causes a particle to be reflected like this now in classical mechanics no matter what happens this ball is not going to end up on the other side of this barrier the only way it could do that is if it went around it or it broke through it but if you say that the particle is going to move in a straight line and it's not going to break through it it means that in classical mechanics classical physics there's no way it can get through it but what's weird is if you shrink everything down to a smaller scale that's not the case so for example let's again say this is now the size of an electron well even on the quantum scale if something's pretty thick you're gonna get a pretty close to zero probability that you're ever going to measure the electron on the other side of this barrier but what happens is if that barrier becomes very thin there becomes a nonzero probability that you'll find the electron on the other side of the barrier without ever having broken the barrier so what that means is on a quantum scale sometimes elec Tron's can just go through stuff and quantum tunneling is interesting because no matter how impenetrable your barrier is it doesn't matter because there's always some nonzero probability that a particle is going to end up on the other side of it when you measure it as long as this barrier is thin enough so the particles that we're going to be using for our experiment are photons and the impenetrable barrier that we're going to be using is a reflective surface now instead of using a mirror for our reflective surface I'm going to be using the boundary between water and air now the boundary between water and air can act as a hundred percent reflective mirror because of the differences in the index of refraction of water and air so when you're passed a specific critical angle and you're shining light out of water what happens is that light doesn't actually leave the water but it just reflects off the surface and goes back into the water and this is called total internal reflection this is how fiber optic cables work as well you can show total internal reflection even just using some jello and a laser [Music] you can also show this total internal reflection using a laser with water pouring out of a spout look how the laser just stays with the water now another way to see this total internal reflection is just to look into a glass of water let me show you now here's a really easy example of total internal reflection notice that as I hold the glass sideways you can see my fingers easily on the other side of the glass but when I turn the glass upright suddenly the size of the glass become like a mirror you can't see anything outside of it so as I move anything down the side of the glass you can see it but as soon as it dips below the surface of the water suddenly you can't see it so basically this water glass boundary here is acting like a barrier it's not letting any light pass through this so no light is getting from my finger to the outside of the glass up through the camera you can see it completely blocks my hand here and again the reason this is happening is because the water and the glass have a fairly different index of refraction than the air around it and what happens in this case because the air has a lower refractive index than the glass and the water it means that the probability of finding a photon outside of here exponentially decays to zero quite quickly so in this case the boundary is actually the air around the outside of the cup so the photons coming off of my finger don't make it through the camera because there's a boundary of air in between my finger and the camera and so you can't see the photons coming from my finger but it turns out if you can make that boundary small enough if you can get that layer of air small enough you actually can see the light so the photons from my finger can actually quantumly tunnel through that boundary layer of air and get to the camera so when I touch the glass you still can't see my fingers that's because even though there's only a tiny little bit of air even when I'm pressed against it you can't see my finger because even though there's just a tiny little bit of air it's still a thick enough boundary that it acts like a barrier to the photons coming off from my finger but now watch what happens if I press really hard and try to reduce that air layer in between my finger and the glass to as small as possible it turns out that you actually can start seeing my finger do you see it so when I just hit the glass like normal see I can push the glass you don't see my finger but if I purse but if I press really hard now you can see my fingerprints and my finger on the glass so this is actually a great analog of quantum tunneling so the only way these photons are getting through this barrier is because I've reduced the barrier that barrier of error to a small enough thickness that the photons actually tunnel right through it another way to do this instead of pressing really hard with your finger you can reduce that boundary of air in between there just by getting your finger wet so now my fingers wet so instead of air in between there there's water and the water has around the same index of refraction as the glass and the water so then you can easily see my finger so having that water on my finger reduces that layer of air very quickly so that the photons from my finger can get from my finger to the camera now this happens with any object not just your finger and it doesn't even have to be wet so I have just some silly putty here you can see if I push it hard enough you can see it on the other side of the glass but if I don't push it hard you don't see it and also to show that it's not just my finger being wet that's getting it to show up on the other side of the glass I'll put this barrier in between but if I push hard enough and squish the air out you can still see my finger so again it's not because my finger is wet my my fingers not even touching the glass it's because I'm squishing out enough air and so it no longer acts like a barrier and so the light can pass through it so next time you're at a restaurant you notice that you can only see your fingers on the glass when you're holding it tight you can start up a nice conversation about quantum mechanics at the table now the experiment that I've done here today was with photons but you can actually do this same thing with electrons as well so even real electrons can tunnel through stuff except it's just a lot harder to show in experiments because electrons have a lot smaller wavelengths than photons and so basically you need something that's extremely thin in order to show how electrons can tunnel through it now this can actually pose a problem in the semiconductor industry on the scale that we're now building transistors when you have two conductors that are close together and some non conductive material in between no matter how good of a resistor that non conductive material is it means that some electrons can still get through it no matter what you do in fact even if you had a perfect resistor if you get these two conductors close enough some electrons will just go right through it even though they never actually went through the non conductive material and thanks for watching another episode of the action lab I hope you enjoyed the video if you did remember to hit the subscribe button and remember to hit the bell so that you can be notified when my latest videos out and get right on watching it and check out the action lab comm for the action lab subscription box and you can check out the link in my description for the action lab experiment book called extreme garage science and thanks for watching and I'll see you next time

Channel: The Action Lab

Views: 3,173,018

Keywords: quantum physics, quantum mechanics, wave function, quantum tunneling, double slit, how to, home science, quantum physics mit, quantum physics for kids, quantum mechanics chemistry, quantum tunneling explained, the action lab, action, lab, science, pbs space time, space time, home science practical, home science experiments, the action lab spider, the action lab black hole, the action lab stretch armstrong, the action lab vacuum chamber, the action lab magnet

Id: kvSlaIwUCuk

Length: 10min 1sec (601 seconds)

Published: Fri Oct 11 2019