I did the double slit experiment at home
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- čas přidán 10. 11. 2022
- Supported by Screen Australia and CZcams through the Skip Ahead initiative.
Safety and where to get the supplies:
I would love for you to try this experiment but please be careful with the lasers. If you're going to buy a green laser then it's crucial that you buy a proper one. Green lasers emit light a lot of invisible IR light and in cheap lasers this often isn't filtered out well. Blue/ violet lasers can also be dangerous for another reason. Our eyes are terrible at seeing these wavelengths, so the laser will look much less strong than it is, which means you might be playing with a dangerously strong laser without knowing it. Red lasers are generally the safer bet. I saw the effect I was looking for even when I used cheap ~1mW red lasers, so it will still work for you!
If you'd like to invest in a nice laser though, this article has some trustworthy green laser brands: www.planetguide.net/astronomy...
Another way to buy lasers that are eyesafe is to get them from school science lab suppliers.
(Note: in some countries it's illegal to sell lasers over 1mW. Please check the laws where you live. In the USA the limit is 5mW)
The smoke machine I got used glycerol. I’m very suspicious of breathing in that smoke though, especially since the room can't be too well ventilated or it won't work. Fine particulate matter is a serious health risk in general so even though glycerol is nontoxic I think it may still be hazardous to inhale. I recommend wearing an airtight n95 mask or similar while doing this experiment.
It found it a bit tricky to source the double slit cheaply in Australia- your best bet might be a science lab supplier. In the USA you can get it on amazon though.
Video credits:
The beautiful animations in this video are made by Kathy Sarpi: kathysarpi.com/
Thank you to Screen Australia and Google Australia for funding this project, and to the wonderful people at Screen Australia who helped me throughout the process.
Thanks also to all my beta testers (aka friends)!! - Věda a technologie
If there are variations you’d like to see, let me know, I’ll film them as a short :)
If you rotate the splits 90 degrees, does the pattern appear vertical? I've always thought it odd that these experiments always produce patterns on the horizontal :) And can you create a 4 sided "slit" to try create a circular or square pattern of interference? Or is that too much interference or not possible?
Nice approachable video. I always felt like the typical demonstrations and explanations don't connect to real-world experience well enough.
I'd like to see your version of the other side of this coin-- what's your approachable experiment to show the particle-like nature? Can you demonstrate the photoelectric effect at home?
Yeah, block all the extra beams except your target center and have another wall behind your current setup to see if more beams appear.
can you do one with a donut shape hole. ofcourse it needs someting to hold it up. so basically a circular shaped obstruction.
Try it with polarized light! (filter the beam to allow only one polarity before the slits)
You forgot to mention the most important point. And that is that the experiment works the same even when you send the photons one by one. The interference could be explained both by light being only a wave and by light being particles that somehow follow a pattern when they bounce against each other. But the magical point of the double slit experiment is that sending photons one by one, the interference pattern arises in the detector screen even when there is no possibility for the photon to interact with any other photon.
If i remember correctly, the Heisenberg's uncertainty principle can bring it back to particle behaviour. If the photons are observed, they behave like particles again.
OK, wait a minute!
Is that just even possible? To shoot only one photon?
The reality of multi-dimensionality being visible in photons behavior is an interesting thing to think through. The wave isn't all within our 4 dimensions at any given point in time and that wave only interests our dimensions at one point at a time.
@Luiz Fernando Only if you're not observing it/them... :)
@@luizfernandonoschang8298 yes
Einstein said: “ It’s a miracle that curiosity can survive formal education.” . It takes curiosity to be able to do science. Keep up the good work.
And?
You're the first person that has shown this without graphics. I love it.
Yeah, I googled double slit experiment but like nobody was doing the actual experiment lol
If you send only one photon, it’s almost impossible not to use graphics
Outstanding! By far the most definitive example I have ever seen.. and I am 60 yrs old.. Wow.. well done young lady.
This was fantastic. I love your skepticism. It's amazing to see a physics PhD admit they're not entirely, viscerally, convinced by the wave theory of light, and then work out whether they can find a way to convince themselves either way. It is seeing the scientific process in action, and it's a beautiful thing. Thank you.
It's called "scientific method"
@@BobbyT-yj1cw naaaaa
@@BobbyT-yj1cw it is how it's called...
She's not a gatekeeper, yet.
@@viola0lividobased
You literally woke up my curiosity over quantum mechanics which I buried long ago for my software career. The demo of double slit experiment is like never before. You're the main reason I bought QM by J.Griffiths textbook a year back. You inspired me a lot. Keep up the amazing work. Love you.
I’m so happy to hear that! Thank you for your lovely comment :)!
Is there a Patreon Page or any other way so that I can support you?
@@kunk6818 aww! I don’t have one at the moment but I am planning to set one up :)
Do Shankar principles of QM after griffths
@@mastershooter64 Thanks for the recommendation.
Absolutely marvellous! You can be taught by a teacher, a lecturer, through a book - but nothing brings it to life like doing the experiment yourself! Thank you for taking us on the journey.
This is one of the best (if not the best) video I've come across that explains the wave/particle duality in a way that even a layman can understand. Well done!
How do you figure? She didn't even do the other half of the experiment with single photons that makes it so mind bending. Maybe I missed it, but did she mention anything about how observing the light changes its behavior? Did she mention how photons can behave like waves even when you fire them one at a time, and how the photons take random but probabilistic paths when not observed? I honestly don't think she even understands the experiment herself.
@@MrFreeGman Take it easy, man; this is just a home experiment. Making equipment that can fire a single photon is costly (at least from what I googled.)
If you disagree or think there is a better way of demonstrating this, please do a video. Don't be bitter.
@@miki_9034 That's besides the point. The experiment is incomplete and boring without showing how photons can behave like waves when they're fired individually. It's got nothing to do with being bitter. This video is just getting a lot of undue praise from people who have no idea what they're talking about.
@@MrFreeGman You sound like you're a physicist. That might be why you're disappointed with the lack of depth in explaining the particle side of light, and I understand that. The reason I loved the video is because she dumbed down the experiment for a guy like me who is not a physicist and within my budget ($20 - $50)
@@MrFreeGman That's just a different experiment with the same set-up. And I think the observer effect of it might be simpler to do with electrons anyway since they're probably easier to fire one at a time than photons. The experiment wasn't meant to show the wave collapse, but was a demonstration of light's wave-like properties. The experiment is in no way "incomplete", you just misunderstood the purpose of it.
As a PhD student in experimental physics it was fun for me to watch a theoritical physicist discovering that experiments are fun! :)
Yes!! I can’t believe that I hadn’t tried doing this myself before and I only worked on pen and paper. That stuff seems so dry now compared to playing with lasers
@@LookingGlassUniverse Indeed, seeing physics happen with your own eyes opens up entirely new perspective! It is funny when you realize that all experimental physicists have to do theoritical analysis but theoretical physicists never do experimental work. You just broke that barrier! Hope it benefits you in your academic life.
yea but lab reports 💀💀💀
@@mastershooter64 They're a part of real life work. As an engineer that's one of the end results of all work I do: design and run the experiments, analyze the data, then write it up in a final peer-reviewed report.
@@LookingGlassUniverse This reminds me of how there were two camps in school. One camp were the math or physics majors, the other camp were the engineering majors. We all had to take many of the same classes and we clashed (that's an overly dramatic word) over wanting more theoretical examples vs more practical examples.
So...another thing we've proved here is that engineers really do have more fun.
The ability to see something physically and practically that you've only seen or heard theoratically is such a surreal moment like THIS is infact a real thing, it exists, I am seeing it with my own eyes and not just some mathematical equations/models, as someone who is curious about literally anything I get my chance at, this was pretty amazing
If you want to see diffraction effects with your own eyes with no experimental equipment, just put two finger near your eyes, look at the space between them, then bring the fingers together, when they're close enough the diffraction effect starts.
You like plants?
That's a pretty lame attempt, dude.
Heh. Same thing when I looked through a telescope at Saturn. My knowledge had always been indirect, from some sort of a storage repository. Books, TV, Movies. But then my wife got me a decent telescope. It was a revelation. No camera. No screen. Just me and this celestial body in the same moment. A real mind opener.
@@ericscott6447 What size objective lens/mirror do we need for that feeling sir?
I really like how you personalized this experiment and revealed how you now can start to see the wave character of light as real from getting your self directly involved and finding the facts for yourself through direct observation of real experiments in real time etc
As someone who has spent way too much time thinking about the double slit, this was an amazing video. Thank you.
It was wrong. Consciousness or the observer actually does not collapse the wave function.
It happened bc of the measurement device used. See Neil degrass Tyson double slit. It was all bullshit. When they measured it the measurement was light which changed it not consciousness.
I don't write comments very often but to this one I really had to. 14:05 and 14:20 are simply jaw-dropping. You are really a very good experimentalist, I never really imagined that I could see light as a wave with plain eyes as it propagates. Thank you very much, it was simply a perfect visualization.
Thank you, this comment means so much to me. I started thinking about this video a year ago and at the time I only knew about theory but I had no idea how to do real experiments. It’s been such a journey even to get to the point where I can do this ‘simple’ experiment. Thank you for your kind words
@@LookingGlassUniverse I'm very glad that you felt so 😊 Keep up the good work 🖖
@@mfatihakal6635
* Plain eyes.
Or maybe you have cat pupils. Heh.
@@dahawk8574 Haha, you're very much right. Some words don't let you go when you spend some time with them. Corrected :)
@@mfatihakal6635
Speaking of cats, I am wondering if Mithuna's next in this series will be...
'I killed my cat at home'.
Yikes. I'm sub'd. But concerned.
Hah.
Your enthusiasm and curiosity is infectious. I love seeing people build their experiments at home, getting incredibly educational footage and sharing it with the world. Wanting to follow that light back was clever, and I finally got to see the waves.
right?? I keep holding myself from clicking the × button because she made everything so interesting in every second if the video.
@@twitzmixx8374 @ Light is both a particle and a wave .
That's why human beings are both a body and a spirit.
put me through the double slit and what happens is...
You absolutely MUST do a follow up video! You MUST fire the laser through a sheet of darkened paper, add another sheet, then another sheet, allowing the light to become dimmer and dimmer, until only one photon at a time is making through the darkened sheets of paper. You will need a very, very sensitive photographic plate to detect single photons. But if you do this, you will find a single photon can land on the photographic plate at some random location in the form of a dot on the screen. Then, if you fire one at a time millions of time over, you will be shocked to find the interference pattern builds up one at a time. Your experiments are good ones, but I want to point out that the smoke is not necessarily illuminating a wave of light interfering with itself. The smoke can be viewed as if it is illuminating many trillions of single photons, all traveling within multiple beams of light, and these beams are all compromised of single particles. The particles follow a path which is seemingly non-deterministic but still at least follows the Schrödinger equation quite well. The Schrodinger equation mathematically treats the path of each photon like a kind of “wave of probability” which determines where the photons are able to land and the likelihood for all of the possible landing destinations and paths that can be taken. That mathematical wave describes the likelihood of all possible paths, and is called a “wave function." The wave function is said to interfere with itself after fanning out from the double slits, causing a pattern of light and dark fringes which can be interpreted as wave interference, even for a single particle or photon, because the wave function is describing many 'possible' paths simultaneously, yet all paths are describing the same particle. So in this way, the wave function is like a mathematical tool which describes places where a single particle is very likely to land and places where the particle is very unlikely to land. Photons can be viewed as particles even after fanning out from the double slits nonetheless. They can be viewed as traveling in beams, not necessarily waves, while still accounting for the light and dark fringes. The individual particles within a beam can only follow paths allowed by it's wave function however. In this view, the middle bar of the double slit serves as a point of origin for a "repeating shadow" which displays as dark fringes from regular repeating angles, where all light fringes are beams of photons (particles) which are pivoting from the openings of the slits, and all dark fringes (which are merely shadows) are pivoted from the middle bar in between the slits. The dark fringes or "shadows" are regularly repeating because the two slits are spaced at equal distances from the middle bar. Someone will ask, why should the photons ever pivot from the slit openings and fan out towards the left and right sides of the photographic plate in the first place? Someone will say, if photons can be viewed as particles in the double slit experiment, then we should always find a double-line pattern directly behind the slits. Why don't we?... It is because of Heisenbergs Uncertainty Principle. Here, most people misunderstand that it's just the speed and location of a photon which cannot be known simultaneously. But the more accurate truth is that - speed, location and thirdly, the 'direction' also, cannot be known simultaneously. We do already know the exact speed of a photon, which is always equal to C. We can also know the exact location of the photon if we create a single slit that is narrow enough to quantify it's location at the moment the photon passes through. But by knowing the exact speed and by narrowing down the exact location of a photon when it passes the slit, we will have sacrificed the exact "direction" of the photon after it emerges from the other side the slit. So when the photon exits a single slit, or of course any double slits, the direction of that photon will be completely undefined by the universe and so the photon shall change trajectory after the slits and be aimed at any 'possible' location on the photographic plate. None of the photons land on the dark fringed bands because in this view, the dark bands are caused by the middle bar which simply casts a repeating shadow behind all angles that are not possible. In this way, we can account for the light and dark bands as beams of particles, rather than waves. I’d also recommend/request that you do a follow up study/video which explores the nature of the photoelectric effect! Here we learn how Einstein models light as a beam of particles, rather than waves, to explain the observations of the photoelectric effect. He eventually won a Nobel prize for this insight because it essentially proved that it was impossible to explain the photoelectric effect when modeling light as any kind of waveform, but instead could be readily explained by viewing light as a beam of particles. You think you’re amazed so far about the properties of light? Hahaha! You’ve only just begun to dive down the “what is light” rabbit hole.
Fun reply with a lot of great insight, but everything you describe is just a theory. There is no definitive proof of the "pilot wave" theory. Yes the individual photons will accumulate into an interference pattern. But, as of 2024, no one truly knows why! Lots of competing theories, but it will probably be a long time before the next big breakthrough that unequivocally proves what is happening.
This is correct - her experiment is incomplete at this point. Needs to go much deeper.
She knows this. She's just showing us an easy way to do the experiment at home so that we can visualize the phenomenon with our own eyes.
@pingpong9656 I wouldn't call this experiment incomplete. It is pretty much complete although simplified. The original double-slit experiment was essentially done the same way. In later versions of the experiment it was performed with individual photons. It was even done using other particles and even molecules which surprised me.
Pairs of single photons / quantums of light are produced by a special crystal.
But what should it say us?
Think of a photon as some soap bubble. The membrane is the wave front. You can seek it und when you have found it at some place, the bubble disappears. You get some local effect. Without further interaction it will continue to spread out from that point.
@@pinkeHelga I love the bubble analogy, but it implies that if we keep making more photon bubbles, then all the bubbles will just pop at the same location every time, at whichever object is located closest to the bubble... Here's another analogy Neil DeGrasse Tyson once offered - Photons are like shouting words at a crowd of people. But the first word gets heard by only one person strangely, while the second word gets heard by another person in another location, the third word by another person in a different location, and so on. All of the words are shouted in the same direction, but the sound waves fall on randomly located ears, the location seemingly non-deterministic, or at least not determined by any known physics.
you have no idea about how much this video changed my perception of light. thank you so much. your curiocity is appreciated
Love this video! Your choice of books for holding up the ripple tank perfectly summarise the journey you are taking us on to understand the weirdness of reality. Well done! 💗
hello :)
Agreed! And my copy of Griffiths just happened to be right on my desk, next to the keyboard, as I began this video!
Which dimension are you talking from? lol
Summarises*
Wow! I was wondering whether it's you (tibees) doing this video, but younger. 😋
My intuition for why diffraction occurs comes from Huygens' principle - it's the natural tendency for light to radiate in all directions. Light traveling as a beam is actually a very uncommon state that is caused by the interference of different points in the wavefront. As you block parts of the wavefront you remove this interference and the light radiates spherically again.
Yes, huygen's principle seems to be the the right way to think about it! But what I don't understand is, given huygen's principle, how do laser beams stay so well collimated in the first place? What do you think? I'm planning on just sitting down and working it out for my next video
@@LookingGlassUniverse At a large enough distance even a laser beam will become spherical, but the distance required depends on the wavelength. How well collimated the beam is to start though depends a lot on how the laser cavity is designed.
Having now watched the full video, I find it interesting that you initially preferred the photon picture of light. For me it was the complete opposite: I found the photon picture of light so confusing that I chose to do my PhD in quantum optics just so I could understand it better. So far though it hasn't worked and I dislike photons even more now. The main thing that bothers me is that the way we commonly talk about photons is very different to how Fock states are actually defined. For instance: in the double slit experiment, its not that photons are coming out of the laser and randomly choosing a path to take. A photon in this case is an excitation of the entire diffraction pattern.
@@LookingGlassUniverse I think the laser's light is so focused because only the photons in the direction the laser is pointing receive constructive interference. The mirrors in the laser are shaped so that all photons hit it with the same phase and they are only constructively interfering in the longitudinal direction implied by the two mirrors. There is nothing more "natural" per se about light to radiate in all directions. Natural light sources just don't have a preferred direction of emittance. The reason why a straight light beam diffracts at a sharp edge is due to the uncertainty principle. If the location of a photon is precisely determined (as in "it is just about not blocked by the edge" then its momentum (direction) becomes very undetermined. Hence the spread into all directions.
@@CyberMongoose I know, it’s been driving me crazy! What the hell is a photon?? I used to think it as point like, but exactly as you said, modes are not at all point like. I’d love to hear more about how you think of light. If you’re down for it, send me an email to looking.glass.universe at gmail
@@LookingGlassUniverse Also keep in mind that visible light is made of wavelength extremely small compared to the diameter of the beam. At microscopic scale, the beam looks like a massively large plane wave. If you try to generate kilometer wide waves in the ocean, you will find that they don't spread very much, very much alike lasers. If you try to make a very small (microscopic) laser beam, you will have no choice but to see it spread out.
I’d love to know why the light only scatters in one plane, or what would happen if you added another horizontal slit. There’re so many variations, it’s amazing
What if blockers are something sphere and in flight
if you add a horizontal slit you get a cross with the interferance pattern on it i tryed before =)
en.wikipedia.org/wiki/Arago_spot@@lUnderdogl
this is genuinely one of the best science explainer channels around
Brian Cox.
I’ve watched many videos on this subject before, but this is honestly the very first one I’ve seen that has helped me gain the most understanding about the double slit experiment…so, thank you for that! What an excellent video.
I love all the way you "blocked" the laser (none, full blocking, right/left half, hair, double split, etc.). I'm looking forward to future experiments! Finally, thank you for mentioning laser safety. Laser power has gotten crazy out there!
I completely agree about the lasers- it was genuinely difficult to find lasers that I could trust were safe. All the labels on lasers mean nothing because they’re terribly regulated.
@@LookingGlassUniverse Even worse, the same applies to safety goggles! Most are as good a PPE item as no goggles at all. On the very first search page, there are googles with non-existing rating "OD 4+" without any mention of wavelength range. For 14.99, the price of cheap sunglasses. Yeah, right. And add the lack of training to that, people think that donning even real goggles gives them the Superman's eyes.
Gosh, you can buy a 1.5W blue laser on Amazon or eBay for under US $200! And this wavelength is quite energetic, not yet ionising, but certainly able to wreak royal havoc on fragile organic molecules even before cooking tissues thermally, so the usually considered class 2 limit of 0.25s eye exposure likely may not apply. They should be handled as class 3B-in a controlled lab... Not the thing I'd dare to even turn on without proper setup. It has enough power to bounce off only slightly glossy black surface and still blind anyone around or even outside the window.
@@cykkm
Damn that's nuts. I remember messing around with only 3B lasers. I did by some supposed match burning laser on Wish a few years ago, but it's only a 3B blue laser. Maybe the UK has better laws in place, as I remember someone telling me that you need a license to buy some of these powerful lasers and they have a very legitimate use in astronomy.
@@Competitive_Antagonist Yes they are used in astronomy, yellow wavelength range (Nd compounds). These are much more powerful. Google "adaptive optics." You've likely seen the stock footage of observatories shooting a bright yellow ray up the sky. But they are mounted on the telescope, already a dangerous machine (and expensive, too) with only trained personnel having access. There are many legit uses in research, not only astronomy.
3B is "not only"; it's a very dangerous thing. If you want to operate it confidently, take a safety course, and you're totally fine as soon as you're following the procedures and get PPE from a reputable vendor (wideband goggles are in a $100-200 range). The 3B safety class is defined as, IIRC, causing "permanent vision damage regardless of exposition time, and possible skin burn" unless properly handled. This label is not about power, medium, wavelenght or anything, it's only about standardized safety procedures. Different countries and states have different rules, but generally the idea is a windowless facility with a warning light at the door when laser is in operation, and only trained people allowed in, OR shooting them up the sky with safety in place preventing anyone getting close to the beam closer that X (a meter or two), for light shows. FAA permit may be required for the latter (Fed. Aviation Admin.); I never did this, I don't know, only guess. Here in California 3B and 4 handling requirements were the same 20 years or so ago. I don't work with them anymore, now daughter does. :)
Class 2 and above are illegal for sale to general public here as separate units, but it's not enforced for internet orders. It's not a big issue, in general, and law enforcement resources are limited.
ADDED: I think licensing discourages responsible experimentation at home. Come think of it, regular tools like a wood-chopping axe are even more dangerous if used improperly, but we don't license them. And handguns are legally sold at every corner. Safety education and raising awareness is a more productive approach.
@@LookingGlassUniverse Perfect demonstration of why we need proper regulation; companies will do whatever they want at anyone's expense to maximize profit.
How is it possible that it is the first time I see a video in your channel? I absolutely love this. You are amazing and deserve a much much larger audience! Thank you for being here on CZcams and sharing your love for science.
Everyday before high school i would smoke pot in the shed on the side my house. The shed was small and had 2 sliding doors that came together in the middle. There was always a small gap about 1/4 inch between the door panels and the sun was just rising over the horizon straight across from the shed. I'd sit on one side of the shed and blow smoke into the light. The light passing through the smoke was one of the coolest things I've ever seen. It was like taking a 2D plane out of a 3D or even 4D cloud. It's hard to imagine unless you've seen similar yourself, but I still remember it 25 years later. This reminds me of it. Go out and try it today!
This was one of the coolest physics video I've ever seen! You took what is common to any enthusiast and presented it both in a new and interesting way, but also in a way that can be replicated easily at home! Freaking brilliant!
Didn't people learn about it in school? It took me back to school. I guess my science teachers in school were really good 😊
👍
OMG. She hadn't a clue. Didn't even mention that the interfering, pattern collapses when observed. Oh dear! Oh dear!!....Don't try to fix something that aint broke, should be her motto. Terrible presentation. Full of holes lol
Everyone knows light acts like a wave. What is surprising is to see particles act like waves, or for light to act like particles. I didn't find this video impressive at all.
@@hhf39p I'm sure this video was not produced with the intent to impress you.
Love the idea of using a single hair! It is so much simpler and clearer than the double slit.
I tried to show this effect for a science fair when I was 9 or 10 (almost 30 years ago👴) after reading some book on QM. But, it was impossible to replicate with what I knew back then (books would show an incandescent bulb as the light source 🙄).
Well, now I'll come up with an easy to carry setup and I'll tour around my family and friends homes showing them how cool this is. I've been waiting for this for too long.
You must be joking. She was all over the place, and incoherent. Can't beat the original double slit experiment! Light is a wave and a particle when observed. Which she didn't touch on. Are they giving away PHD's to anyone these days?
First video that actually showed real proof of it. Maybe I'm bad at finding things, but you totally nailed it and blew my mind away. Thanks for making and sharing this.
I've seen that pattern and didn't realize what I was seeing with my own eyes. I knew about the double slit experiment. I even knew a lot about RF waves and interference patterns. Somehow this tied it all together in a way that made me tear up. Thank you!
Not sure if you'll notice, but I have to say this.
I have looked for something like this for years. I'm in love with quantum physics and can't pull out of my mind all of this. I was simply vaping in my room, turned on my laser pointer and noticed this, clearly, but never really saw anyone noticing this as well. Moreover, all of the videos about double-slit experiment were strictly about "life isn't real!!!!!", so it's actually a big relief to see this.
Thank you a lot.
So clever and simple. As a teacher for some 40 years I can honestly say your talent for communication an devising simple demonstrations is considerable. Good luck for the future - you'll make a difference to so many students ! 🌞
Except that she's dead wrong about what she thinks are light waves. See my post above. She is astonishingly clueless and sadly misleading the unsuspecting public.
wdym there's no post above
Stop slobbering.
@@Yogesh-kr7bo Well, the problem is the photon also acts like a particle when it's absorbed or emitted by an electron. She completely avoided that issue. Lots of atoms absorb and emit light at specific wavelengths, and that light is absorbed or emitted by electrons as their energy level goes up or down. A photon can be treated as a particle or a wave, it acts as one or the other, depending on what you are observing.
Electrons have a wavelength too: From google: Louis de Broglie showed that every particle or matter propagates like a wave. The wavelength of a particle or a matter can be calculated as follows. Thus, the wavelength of electrons is calculated to be 3.88 pm when the microscope is operated at 100 keV, 2.74 pm at 200 keV, and 2.24 pm at 300 keV.
@@morpheus6749 I searched all 1146 top level comments for your post and couldn't find it would you mind to repost?
That's probably the coolest DIY experiment I've seen on CZcams, and those visuals.. wow
Really have to wonder why the simple addition of smoke to aid in visualizing this phenomena has not already been presented to us by our brilliant scinetists doesn't it?
This visual you've demonstrated is awesome. Thanks for this!
Well, that was the most informative explanation of the double slit experiment I’ve ever seen. I’ve always been confused about this for the same reasons you mentioned. Well done. I hope you do more along these lines with light.
Very cool! I'd recommend doing some experiments with polarization filters. When you take two together, turn them so they become black and then put three together and turn one and it makes them transparent, that really blew my mind.
Will do! Thanks :)
Visualising that with the smoke machine would be really interesting.
Ah! The good old quantum eraser
When you use three, it only works if you turn the middle filter. Each filter can only twist light so much before it’s completely blocked.
If you use two filters to block out all the light, merely adding a third filter over them will never get you back light, no matter what orientation you rotate that third filter.
Imagine if schools accept you if your accent is similar or reject you if your accent is too dissimilar. You can therefore only attend schools that are nearby otherwise your accent will be too different and you’ll be rejected. But attending that new school changes your accent so now you can attend an even further away school. So you can eventually attend a really far away school with a completely different accent by hopping through intermediary schools that slightly twist your accent little by little.
@@TheLazyVideo ah, so the light cant twist 90 degrees between filters, but it can manage ~45
Great video! The subject is presented in such a grounded manner while still being accurate. It allows the uninitiated to be introduced to the topic while keeping the mathematics at bay.
this is the first time i see the experiment in real life and not throught graphics. amazing job
Great video! In my third year physics at Monash Uni I did the single photon double slit experiment. It’s mind bending and I highly recommend you check it out. Especially if you are loving the wave nature of light. In the experiment you get to see for yourself how even a single photon of light can become a full wave and produce the same result as the double slit experiment.
I’m no longer in the field of maths of physics, but I still remember that experiment. It changed my view of the universe. Great to see some great Australian physicists on CZcams! Keep up the great work.
That must have been awesome! Whenever I hear about the single photon double slit experiment I remember that when the photon is measured for position, the waveform collapses. Yet I have never been able to find actual video of this happening, only "simulations" or "replications". Is there any video out there that you have come across?
@@IFY0USEEKAY This is the single photon experiment: czcams.com/video/e30BuTnhJng/video.html
here it is with an explanation of what you're seeing: czcams.com/video/_MpvDAQrKbs/video.html
I was looking for a comment about this. The real quantum magic happens when you do it with just one photon.
Did you really do a single photon, or did they lie to you with maths?
czcams.com/video/I9Ab8BLW3kA/video.html the single photon experiment starts around 5:46 - showing the wave nature of light and the quantum “collapse” on measurement
So cool that you got the other beams to become visible! I've worked on this at home myself and it is absolutely worth doing, but I've never actually seen the other beams and figured they were just too dim compared to the main split beam to register optically. Unrelated: I always thought of waves as the "real" concept and particles as the "abstract, for math purposes only" idea. I wonder why our brains do that.
Do you mean beams on the paper, or in the air in transit to the paper? I want to do this at home so should I buy the most powerful laser online?
@@CoruscationsOfIneptitude are you on the electrons don't exist team too? What about atoms in a Bose-Einstein condensate? Does simply changing the state of matter make it so that the atoms themselves cease to exist?
@@CoruscationsOfIneptitude I was actually kinda hoping, for some reason, that you might have something interesting to say that defends your stance that the particle half of quanta is only a mathematical construct. Unfortunately, you decided to stop asserting things about physics and start asserting things about people. If you ever grow out of ad hominem, I'll gladly have a conversation with you about physics.
I've been experimenting with the strobe effect in a small flashlight against several different surfaces. Looking just outside of the direct beam on the surface and without visual aids, I relax my eyes and start to see the different primary colors show up as dots, randomly across the entire area around the center of the beam, as well as up to a foot around the center of the beam. These dots only appear for an instant but constantly reappear in "scatter shot" manner, and don't appear to move or reappear in any organized rhythmic fashion. I've tried this with the flashlight at different distances from the surface, usually 6" up to 5', as well as different colored surfaces. The results only vary slightly, but the light away from the center starts to create very interesting patterns. I don't see this with a solid beam, only the strobe. My eyes have to relax enough so the strobe appears almost solid but I definitely know when I've gotten there, and I actually have to force my vision back into just seeing the strobe beam. Once again to make it clear, I don't look directly into the main part of the beam and I don't have any residual images "burned" into my eyesight after I'm done. At most I'll do this for only five or ten seconds at a time.
Love this! Excellent video that explains the theory and shows the process for others to explore as well. Wished I had found your channel before but so glad I have!
Light has always kind of freaked me out. For instance, you can have an infinite amount of viewers looking at the same spot on a mirror and there will be an infinite amount of different reflections. Or, sitting in your room, every point of light bouncing off all surfaces in all directions somehow resolve in our eyes to fine detail.
Well it wouldnt ever be enfinit becauze the mirror ends and that second thing you described is just your feild of view. Try and focus on your feild of view, its blurry and not that detailed. You cant focus on it maybe because the light isnt all being reflected. Im in my room right now, my green pillow with white spots is in my perifrial but if i really try and focus on it withought looking at it it literally just looks green to me. And the white wall that its agains is in full detail, cus there. Try and take a thin thing like a book and take it as far out of your parifial as you can withought actually loosing sight of it. And just observe it. Think about your eyes too, theyre spherical, what youre seeing isnt actually flat as your brain WANTS to precieve it. Youre brains flipping the image upside down, focusing on the center and if you go agains the own rules of your prain yourll feel a little bit of strain and discomfort, at least i do. Because were actually limited and our brain forms the illution and our contiousness preieves that illution. And everything beyond that is unknown
Of course infinite viewers will be shown in a mirror, because the mirror reflects the light that the electrons in the viewers' bodies emit. Is that so surprising?
Hmm. Sorry terrible comment. Blessed be.
🎉❤🎉
@@charlesbarr3437 no it's not
something i found interesting was taking my first long exposure picture. i kind of took light for granted before this but once i took a long exposure photo in almost pitch black darkness, and it appeared as a sunday morning, i was able to grasp how mindblowing light really is.
Oh my god! Girl I remember watching your channel something like 10 years ago, and somehow it disappeared until just now. A huge fan has been reactivated! I'm really happy to see you and to hear you've done a doctorate. It honestly feels like reconnecting with an old friend. Also, what a nice experiment there. I think I'm going to copy what you've done here! Thanks!
Oh my god, thank you for this adorable comment!! That’s so sweet! What are you up to these days yourself?
Amazing, i have seen so many animations and always wondered what actually happens. Thanks for showing this.
Now I would love to see what it means in reality when they say they measure through which slit a particle goes through.
This is easily one of the greatest videos I have ever watched. You truly are gifted, thank you!
Thank you for making something *real*, something educational, and without any click-bateyness. This is so fascinating.
clickbaitiness* Sorry, I'm anal.
What really breaks my brain is that Young's double-slit experiment has also been conducted using all sorts of things that we generally agree are particles: electrons, protons, atoms, all the way up to large organic molecules (buckminsterfullerene about twenty years ago up to a 2000-atom molecule as of 2019).
Great video and very good explanation!
and they also reacted as a wave or as a particle?
@@vlake8614 they all show the characteristic interference of waves, but are detected as particles.
Like your presentation, slowly revealing the secret. The animation helps your verbal explanation but the real games changer is the video with smoke. Thank you.
Since I first discovered this experiment I've always been fascinated by it, even more so when a new model was set up which if I remember correctly fired one electron at a time with detector plates set up around the device which then changed the outcome.
Its mind blowing, this kind of physics is the stuff dreams are made of.
i just saw this and i am so excited for this series, light is right next to gravity for me in terms of being something so frequent and interesting and yet so little is intuitive and even understood about them. PLEASE DONT STOP
Yes, please continue the experiment with single photon. The whole point is to show the wave AND PARTICLE duality because when observed, they behave like particles, but when not observed, they can exhibit interference patterns.
When not observed, the rarefaction of light is a shell/wave.
When observed, the compression of light is a photon.
Aether's field is wave.
Aether's mediated to center zero point/Counterspace/Nothing is the particle.
Light is aligned Aether.
"Scalable Aether Universe".
Or particles in other universes affect the particles in our universe.
_"when not observed, they can exhibit interference patterns"_ - in the interference pattern, they are observed as well. When not observed, you don't see anything.
What you probably meant to say, is that when the possible paths of the photon can interfere with each other, they show an interference pattern.
“Observed” in the double slit experiment is actually a misnomer… The researchers didn’t observe the photons that caused it to collapse into a particle function, they “measured”… meaning they literally interacted with the wave before it even encountered the slits. Considering that a photon is the smallest unit of anything that we can measure with, it’s difficult to measure another photon without affecting its state/position.
The best explanation I've ever heard of this experiment! Can't wait to share it with my daughters.
This is extremely cool! If you look at the beam without the double slits is it the same “width” or does it get “wider” once you out the slits in the way?
I love this whole thing! I’ve heard so many times about the double slit experiment but never seen it such a practical everyday sort of way. You’re right it really hits the ideas home. This quantum home experiments idea of yours is great. I like that it’s slightly wonky and underproduced. Truly. Wonderful stuff!
A thought:
Does different colours of light have a different interference pattern?
Red should have the largest gaps, and violet the smallest because of the difference in wavelengths. Is the difference big enough for the human eye to see using a double slit experiement?
Great video! This made the wave-particle duality of light a lot more intuitive for me!
Yes the dots are more of less spread out depending on the frequency
Yes, the colors change the dot pattern, and yes, it's visible to the naked eye! White light has a really interesting dot pattern as it's made out of pretty much all frequencies between red and violet, so doing the double slit experiment with sunlight makes a really colorful pattern, kinda similiar to a prism. you can try yourself, with a long dark box with a double slit opening. but it's a bit difficult to get it right because you somehow need to, you know, be inside the box to look at the pattern. you can look it up online if you want. veritasium made one in a video some years ago
This is actually a really good thought: It would not be hard to modify this experiment to have two different colors of lasers mounted vertically one above the other, both going through the same double-slits, so you could both see the difference in patterns on the screen, as well as see the different spread of the individual "beams" through the fog...
Great video. Thanks. Love your enthusiasm.
Why the light creates a pattern horizontally but not vertically?
I mean, many sound waves are omnidirectional, so I would expect that the light waves were too.
I really enjoyed this video, so thanks. At the age of 13, we set up a practical in physics class, and the double slit experiment really confused me. I respected this particular teacher so much because we were encouraged to ask questions rather than provide answers based solely on what we saw. At that age, I didn't realise that we were being introduced to the first glimpses of quantum physics. I enjoyed physics; building a motor from scratch was an amazing experience, although I wasn't a great student compared to my peers. I thank my physics teacher, whom we called 'Planck' (Brian Boardman, his name a 'play' on his surname), and all those who tried to educate me. My excellent physics education enabled me to understand more about the physical world as I gradually moved into the field of geography. Life is an amazing experience. It's worth living. Ad altiora!
Your personality shines! Great explanations!
Wow, I absolutely loved this. I've seen so much content about this experiment, but you managed to teach me a lot and think about things in a way that I hadn't ever before.
I think it's because you're genuinely curious instead of just teaching an "established fact". Someone with your background you could totally expect this to be all drab and rote and just a textbook answer but you're actually digging in and trying to perceive and conceptualize things.
Thank you.
This is the best variation or presentation of the double slit experiment I've seen. Really amazing to see all those beams
Just saw and loved your video. Thanks for making it understandable for someone like me, not having any background on this subject
Wow this is the best video I've seen on the double slit experiment so far... and I've seen a lot.
What’s really cool is I’m now realizing that this was right in front of me the whole time. I have an astigmatism so I see lights like this all of the time. Kind of coming at me in beams, the moment you showed the final experiment it hit me. That’s insane
Same here
You don't even need astigmatism to observe this effect! If you squint your eyes so they're just barely open (a slit!) you will see the light spread out like in the experiment
@@Aiden-ham i actually just did this , and yes squint and you'll see the lines , ngl for a quick second there i thought i was doing something a little bit amazing , you brought my straight back down again , lol
Me too. Since my glasses lenses are made of a material with a high refractive index, they exaggerate the effect, which is most noticeable with near-monochromatic light. Since so many people have been moving to LED lighting in recent years, I've been seeing a lot more of it than I used to.
@@Aiden-ham you just blew my mind. I’ve always wondered why lights look like that. This is insane
This is the first time the double-slit experiment felt tangible to me, thank you for a wonderful set of demos 🌈💖✨
Came here a year after the vid was published, but "It is it's own thing." Thanks for saying that out loud. 😀👍
Why am I just now finding this!? Well done!
This is an outstanding video. You told the two-slit story as a personal journey, with terrific animations and a fascinating climax.
This was incredibly fascinating! Thank you for putting this together, I never was able to quite grasp the double slit experiment before, but this made it really clear.
This video made physics 1000 times easier to understand for me. Please don't stop making these videos.
Jeez lady, you're smart!
I've been meaning to do this for some time, never got the chance. Very interesting to see someone did it finally.
I’m not a scientist but learned about this experiment from Brian Green years ago on PBS. It was such an enigma! I kept following up on the newest reasoning and nothing made sense! This video was almost cathartic. Your explanation was clear and the tests were simple and easy to grasp! Great job!
Any one knows a simple version of this experiment, but with photons detectors behind each slit?
@@manuelfrn I don't know how to detect individual photons at home but it's been done in the lab. From what I've read, any attempt to measure the photons before they hit the back screen eliminates the dotted line effect and instead you just see two spots of light (or one spot with a line through it).
@@ScottFreemire I asked chatGTP and he told me that when you have this photo sensor, it must be placed normally to the light beam direction. When the photon collides with the detector, the photon is absorbed. Therefore it is no wonder that the interference disappears, because now you have just a single slit that lets the electron to pass...
PBS is the BEST source of woke scientism... Great job!
I totally loved it. This is the first time I am able to see the interference pattern of a light wave as clearly as it's usually able to see it in a mechanical wave, like the interference pattern in the surface of a lake generated by two point sources. It's an outstanding work. I'm a teacher assistant at my college and I'm going to suggest sharing your video with our students, I think it is exceptionally clarifying. Congratulations and thank you very much! Kind regards from Argentina
You're the best. I do understand now that I see it in real life experiment, not graphics. Thanks a lot
The animation with you in the boat saying "what wave"? Made me laugh. I think I love you. 😁
What a really cool video! I guess that's the great side of available technology is that people like you can do really interesting experiments and videos like this for the rest of us to see! Keep up the good work.
This experiment never ceases to amaze. What really blew my mind though was that actual particles such as electrons also produce interference patterns. Perhaps you could figure out a way to show that too? That would be so cool! But please keep it safe. 🙏 Amazing videos. I'm already a fan.
Problem with matter is you need the mean-free-path before collision to be significantly longer than the distance it’s travelling. With air molecules around the particles need to be travelling very fast, like “ionising radiation” kind of fast. It’s basically only viable to do the experiment in a vacuum chamber, with a particle beam. Electron beams just need a heated cathode and a plate with a hole in it at, held at a high voltage, but it’s a bit of set-up.
There is a 70-80's italian TV documentary that shows that:
czcams.com/video/tMl9Me2hoLE/video.html
There is an italian TV documentary, uploaded on CZcams, that shows that. Search for:
"L'esperimento più bello della fisica l'interferenza di elettroni".
Electrons are also wave phenomena... Are only like a chunk with position or speed or direction when measured, interacted with. The right amount of energy in a harmonic configuration for there to seem to be one or two or however many electrons when interacted with...
Thanks for the note about eye damage from lazers! I have some from playing with them as a kid, they can be serious if you don't pay attention to what you're doing
Most underrated channel. You deserve millions of subscribers.
This is the most impressive and informative video I've watched on this subject out the dozens and dozens of others! Cheers to you! Excellent work!
Just thought it would be important to note that the results are quite different when using a wide spectrum such as white light. I tried it with white light at first and thought the whole physics community was crazy until I saw it with a narrow spectrum Lazer. Of course that was about 2 decades ago.
Thank You so much! I do not have words to express my gratitude
Excellent demontration for the casual physics hobbyist. Bravo!
When doing this at home I find it fun to turn the ISO (i.e. gain) up to max on the camera and turn exposure time and aperture down. When exposure gets low enough, the image begins to resolve onto individual bright spots. If light were simply a wave then the experiment I have described would always give an interference pattern, just with less and less intensity. Instead you get a random spread of individual dots at a fixed intensity. So light looks like a particle in this version of the experiment. But take a lot of these photos and sum them together and suddenly the interference pattern is back. So in the *same* experiment you can demonstrate that light is interfering like a wave but arriving at the target like a particle.
I must argue that quantization has nothing to do with light being a particle (which it's not). Light is a product of two fluxes. Thinking of fluxes as objects is an attempt to shoehorn the language of classical mechanics into electromagnetism where it doesn't belong.
@@anolakesThanks for the 3rd grade simplification of mistakes made by professional physicists. The people on whom you would rely for your explanation think of light as a "point particle," which is demonstrably incorrect and doesn't even make sense as a physical entity. I would get more into the physics, but that's not really the point of contention.
There are some people who are simply incapable of imagining a universe that isn't made of stuff, so they think everything is a particle and all field and flux behaviors must arise from particle interactions, similar to what you've said. I assert the opposite, that light is entirely made of flux-driven fields and hydrogen (THE atom) is made of light. Ultimately, there is no such thing as a particle of any kind. Physical substance is fundamentally insubstantial.
@@anolakes Okay, Captain Physics. What is the smallest, most basic particle made of?
@@anolakesCongratulations. You've won the CZcams comment section. You may now feel good about yourself.
Light always Wave nature, till you either observe or falls in to screen/object, then it becomes particle. Narrowing aperture amounts to detecting so it becomes particle.
Yes, we take what's been studied and surmised from others works for granted, assuming there isn't more to the story as it were. I learned so much more from your clinical experiments, creative thinking, and results. Thank you for posting.
It reminds me of Side-Bands on a Spectrum Analyzer.
"Third, fifth, seventh & more hamonics.
We used to see these same type of hamonics on, "14 thru 128 track Recording Heads 15 inch on reel to reel systems.
@@Fatdog-Dakind wtf are you ranting on about lil bro
@@talon6268 At the RTS GUAM Tracking Station we had to verify that the Playuback Heads on the Memorex Recorder's were not producing harmonic sigjnals stronger than the real data signal being recordered. Light acts like a sound or electronic wave too so who knows, it could be related.
It has never been so simple to understand this slit experiment and the whole phenomenon.
The double slit is my favorite experiment! That was mazmerizing to watch! Thank you!
This video is worth sharing with all our chem. Engineering / civil / mechanical / electrical undergrad friends !
This video is brilliant. The way you went about setting things up and the smoke screen idea at the end was wonderful; I wish more lab classes actually do the smoke thing to teach polarization. This is why I love physics. Congrats and I look forward to more of your content!
Right?! When you see how easy it is up, it’s stunning that it isn’t done in every high school. I also want every school to go over additive light where they use three different flashlights to show how red and green make yellow.
You might find Theoria Apophasis most enlightning. Go learn about real science there
We did a similar study and published our work on it about about 2 years ago. We have a CZcams presentation on it which you can find if you lookup “light strands not waves”. We came to a different conclusion that this supports particle behavior not wave properties. These light strands are distinct linear tubes of light. Wave interference would create fuzzy patterns. These light strands exist within and pass through hollow tubes. Waves shouldn’t. Light strands can be focally blocked without distorting adjacent or downstream strands unlike what would happen with waves. Would like to get your thoughts on this. There is a link to our papers on the channel. Also have paper and CZcams video on how Poisson spot can be explained by particles, not waves. If interested and have equipment would like to collaborate on doing this experiment with individual photons and hollow tube channels on the exiting side. If particles should see fringe pattern. If wave should see nothing. Hope to hear from you.
So sir from the perspective of waves poisons spot can be explained I guess😅
To better explain my thoughts what I see is that there is no difference in wave and particle I repeat NO difference And I AM NO MAD PERSON if you want I can explain it the difference is External that is environment. Etc
This video helped me realize something that’s long perplexed me about popular summaries of the double slit experiment, specifically the part where the summary says something like “but observing the electron changes it back from a wave to a particle, collapsing the wave function and fixing the electron in space.” From here, many non-experts lark off in all sorts of wild directions about consciousness, time travel, etc. Your video, plus another showing that a real double slit experiment with only a small amount of space between the slits results in a random cloud under observation (measurement), instead of two distinct clouds, made me realize that probably what’s happening is this whole particle and wave notion maybe isn’t correct. Or rather, *in no case does the electron behave like a particle, really.* it’s not that measurement turns the electron (or photon) “back” into a particle, it’s that measurement screws with the initial wave, such that the resulting waves hitting the final measurement board are sort of all over the place, and no longer interfering perfectly enough to develop the interference pattern. It’s not the notion of observation that’s doing this, it’s the mechanical requirement of observation in the first place - to make the measurement something has to interact with the electron, and that interaction isn’t changing the electron from a wave-like thing to a particle-like thing, it’s just changing the “shape” of its waviness. Put another way, it’s not the wave-like nature that’s disappearing upon observation, but literally just the perfect arrangement of wave like natures that result in interference. I think this confusion would probably go away entirely if we could somehow figure out what exactly a photon really is.
Love your work. I like how you’ve demonstrated both how simple this experiment is to perform, and how profound its implications are.
On a safety note: perhaps acquire, and recommend the purchase of a pair of laser safety glasses suitable for the wavelength of laser being used, if it is capable of burning you. They’re way cheaper than new eyes.
Would you care to expound on these implications so I can see what level of reality you have ascended to?
Been trying to understand this double slit experiment/light being particle or wave and I've watched tons of videos about it, your video helped me understand it on a different level. Thumbs up!
Unfortunately, no, this still isn't it. It's a misinterpretation. No waves have ever been observed.
Best visual i’ve ever seen! I’m a visual learner and this makes a lot more sense than the theory of light acting like an abstract probability distribution that only collapses to a single nondeterministic point once it hits the wall. The only thing I still don’t get is that when the light is observed closely, the pattern should collapse back into only two blobs on the wall but here the ripple pattern is still there even after we observe it
maybe "collapse" happens only when we shoot individual photons, trying to determine wich path exactly they choose. In the video, we have a lot of photons, so we are not trying to determine the position of one single photon (so there is no "observation", which is measuring the position of on single particle)
Wait a minute... Did she just proved that what we knew about particles, that they behave like particles when they are observed and like waves when they are not observed, is wrong? Because clearly here, the light spreads crosswise of the board with a wave-like behavior irrespective of observation or not.
@@zevul7870 no, we _are_ making an observation. The smoke that makes the spread-out beam wave visible is an 'observation'. remember that we are still not seeing 'light'- but rather the glow in a colloid that results from them. Think of the smoke as a 3-D detection board, if you will.
Thank you for er, illuminating us on this subject! Seriously, very interesting!
So cool to see this! I studied Physics too, and I don't think I've ever seen these beams. Congratulations for wanting (and achieving) to see it with your own eyes.
Amazing video! As someone who did a science fair project on holography in high school (in my senior year 1982-83), I spent lots of time working with a ruby laser in dark rooms! I'm happy to say I did make a few viewable holograms and won first place. Just subbed to see how the future experiments go!
Just came across this, great video and I love your enthusiasm! :)
Wow! This video gave me a much better understanding of the double slit experiment and the behaviour of light. Altough i've seen lots of documentaires, this made it really "click". Thank you so much, i might do it at home one day and look for myself
If particle / wave duality was not enough (physicists mostly can work with that), the truly crazy issue comes with the next step in the Double Slit experiment. If one reduces the laser’s power then using a photoreceptor detector one can eventually detect just single photons of light. As the name "quantum mechanics" suggest, things come in small discrete packets of energy and for light of a given wavelength there is either a whole photon or none; there are no ”half a photon” or “1.5 photons”. This up turns the seeming proof earlier that light is made of waves. At best perhaps we can accept the idea of a small packet of a wave - the "packet" is the photon and its nature consists of a wave too....
Ok, so now repeat the Double slit experiment with this reduced power laser - what happens? Well logic would suggest that if just a single photon leaves the laser at a time, then it presumably goes through either the left or right slit. Then as there are no other photons in transit for waves to constructively or destructively interfere with, so the single photon proceeds to the end card unaffected. If we could "see" single photons we would observe two spots on the card (one for photons going through either the left or right slit) with just a little spread due to diffraction? ... errr no… that might seem logical, and theoretical & research physics would largely have come to an end 100 years ago...
Instead using a photodetector to measure the spread of photons across the card one finds the same bright and dark bands... In other-words single photons may leave the laser one at a time and yet still interfere with something that our detectors imply is not there. The seeming interference with ghost photons leads to very different suggested descriptions of reality and there is as yet no theoretical or observation proof for either of these:
A) Copenhagen interpretations state that the photons are both particles and waves and that the process of observation (or interacting with other things) forces light waves to change into particles. This collapse of the wave function is probabilistic. If one places a detector at the slits one sees just single photon going through one or other of the slits but then there is no interference pattern seen at the detector card. If one does not “Observe” at the slits then it seems that the laser emits a wave, unobserved this passes through both slits will interact as waves do and the on reaching the detector card then interacts with that to revert to particles randomly appearing at single location given by the statistical probability of where interfering wave patterns would be. This use of language to describe “observing” the photons in such experiments does not mean having researchers consciously being aware of seeing, but just interaction with other things that have their own quantum particle/wave duality (e.g. electrons in the atoms of the card detector), but leads to a number of variations in this explanation.
B) If concept of things seeming to “know” if they have been observed seems spooky enough, the other main group of explanations are based on the Many World hypothesis. In this there are different universes of possibilities and our photon both may travel through either slit in different universes, indeed it does travel through different slits in different universes and these universes then interfere with each other!
I love that you took all this time to find out for yourself. I’ve seen lots of detailed animations and heard really good explanations, but you’re the first person I’ve ever seen actually do the experiment.
Anyway, this is the first video of yours I’ve seen, but I subscribed to your channel hoping for more of this kind of in depth experimentation.
Post-doc confused by her own hair.
Makes youtube video to confuse the rest of us.
Sì siamo stufi di disegni animati. A scuola non sperimentiamo un'acca, almeno qualcuno insegna a farsi esperimenti in casa!
@@-danR Meglio confusi che omologati a dogmi (divulgazioni spacciate per scienza: semmai c'era scienza, sta in chi ha sperimentato, non in chi ha sentito dire o letto!)
I like to think about it as if there's no particle or wave ambiguity, everything is always waves. When they are localized enough they look like a pointlike thing we call particle (collapsed wavefunction), and whether the experiment yields one result or the other depends only on the measurement. A photon exciting an atom into an upper energy state is also a measurement, just not performed by us, and so the waves describing the photons get localized enough for the photon to act as a particle with a discrete amount of energy and momentum to transfer into the atom instead of a spread-out wave which shows no signs of the photon being precisely anywhere in space. In the end the measurement is really any significant interaction with the medium. Everywhere in between the wave is not localized and then it shows "plain" wave behavior such as interference patterns. Note that this also explains why when performing the double slit experiment with "single" photons at a time, the result is the same (interference pattern), and it's because each photon is always a wave until it significantly interacts with something (measurement, collapse of the wavefunction, etc.) so each photon can actually interfere constructively and destructively with itself! It doesn't need other photons to interfere with. Also this is why measuring through which slit the photon went through eliminates the interference pattern, because by measuring we are inevitably interacting with the photon and so its wavefunction gets localized. This is ultimately the Copenhaguen interpretation of quantum mechanics, once you learn about that everything becomes a little bit clearer. But then again, anyone who claims to understand quantum mechanics is because they don't actually undersand it at all lol. This excellent Arvin Ash video explains it in more detail czcams.com/video/YbrxK1XMmVA/video.html&ab_channel=ArvinAsh