Quantum experiments at home: kzfaq.info/sun/PLg-OiIIbfPj3mDFx5zjVPtgiGwZMM4Erw Clarification: I didn't mean to imply that the squiggly wave (gaussian wavepacket) isn't real light. It is! Pulses of light are actually way more realistic than (approximations of) the infinite "photon" states in real life. All I'm saying is that these aren't photons. That's because photons can only have a single wavelength (i.e. colour). In this video I talk more about realistic waves of light versus plane waves: kzfaq.info/get/bejne/q9Vjl9Zhq7zUiKc.htmlsi=l_ygoQ9Jh-etGlGR Here’s an update about my “why light slows down in water” videos in the series. At the end of that video I was optimistic that my simulation kind of showed light slowing down- but it was hard to tell. A lot of extremely kind people offered to improve my code to see if the effect was real. It turned out when they ran it for much larger times, that the simulation didn’t show light slowing down. That means something is fundamentally wrong with my simulation, but I don’t know what. Separately, a bunch of people suggested I look up the “Ewald-Oseen extinction theorem”. That looks very very promising, but not super easy to understand. (If you understand it, I’d love to hear about it!) All up, I’ve decided to put that question out of my mind for a few months, since I’ve spent a lot of time on it. I do want to revisit it though. Thanks everyone for being so supportive!

I'm a 67 yo electrical engineer, going back to try to learn all of the physics that I was supposed to learn in college. You're asking the exact questions that I've been asking. But, you're making MUCH more progress than I am. Keep up the good work... this will serve you well... and you're doing a great job helping the rest of us... young and old!

I appreciate the fact that you are presenting material that isn’t the same recycled rehashed “quantum mechanics is weird, look at this double slit experiment etc“ that lots of other people just present over and over.

Please don't abandon the experiments, they're amazing to see when they work as you journey from theory to reality! Love this series so much, got me thinking and kept me up late more than once.

I get excited when you tell us about a way you WANTED to do a thing because I know I'm about to see critical thinking in action and that's one of my favourite things about your channel. Too many people are too ashamed of not getting a thing right the first time to show their diagnostic processes and that's a real disservice to the world when you're bright enough to solve problems and would rather act like you're so smart that you never have problems to solve instead of showing how to think through things and never give up on the learning process.

SO EXCITED to hear you reference Huygens Optics because... that's been the only KZfaq channel discussing light that has made any sense to me. The slit experiments, in particular, seem to be a jumbled mess of contradictions when KZfaq animators try to explain them. I'd love to see you and Jeroen collaborate; at the very least, would love to see you walk through some of his videos to tease out the harder points.

You're always so chipper, it was kinda nice to see the frustration that comes with setting up and attempting an experiment.

I did that photoelectric effect lab for undergraduate physics lab. Had to be done overnight as you're measuring pico amps and nothing, nothing can be allowed to interfere with the measurement process. The first time, at 2:30 am, a large (in the US) semi-truck (lorry) went by the building, vibrations ruined the trials for the night. The following weekend, at around 3:30 am, some grad students decided to stop by their offices to pick up some books. Vibrations from the building elevators killed the experiment. Third time's a charm. Finally. Tough lab. Not as invasive as the Rutherford experiment. One entire floor of physics building had to be cleared for most of the day to do that lab (I didn't choose that one).

Nothing original here, just emphasizing what others have said in the comments - I love this series. I can't get enough of these videos. Unlike other physics channels, I feel like I am going on the journey with you, not getting blasted with look-what-I-know content. Your channel is pure gold! I actually recreated a couple of those experiments at home and while simple, they do bring about this feeling of awe like look, its really true!

I love Feynman's "it comes in lumps."

I studied Theoretical Physics in uni, but never finished (got too distracted by too many interests across all of science), and ended up as a software developer. Fast forward 30ish years and my interests in all sorts of sciences never disappeared, including Quantum Mechanics. I definitely accept the results of QM theory shown in counter-intuitive experiments - but I never "got it". And then you come along and with some simple diagrams and a few steps of explaination, make the whole wave/particle duality "click" in my mind.

Subbed. This vid has a very "veritasium" vibe to it. Have never heard things explained like this, and you answered questions that have lived in the back of my mind for years.

I am genuinely happy to see that you give us your own explanations, using words and phrases that you came to by your own reasoning and experimenting (even if the experiments "failed"). Most people only repeat textbook phrases like a parrot, without really understanding them (yet they think they understand them). This series is a very fresh look into the topic and I highly commend you for the work you put into it.

Very beautifuly explained. Thank You!

22:05 Another good explanation for why is because of Heisenberg's Uncertainty Principle. This states that the uncertainty in the energy and position of a photon are related, and the more certain you are about one, the less certain you become about the other. It's related to the usual principle between momentum and position because, when factoring in special relativity, a photon's momentum entirely determines its energy by E = pc (energy-momentum relation in SR), so the uncertainties for both properties coincide. So the reason why you get more colors after a measurement is because, when measuring photon position, you decrease the uncertainty in position and increase the uncertainty in energy as a result. Since you are less certain about which energy the photon is at, you get a superposition state of all possible energies that photon could be at, weighted by the probability the photon is in each energy state, which is where the extra colors come in. It even also explains why an infinite light wave is not practically possible, because this would imply perfect certainty about the energy of a photon and thus infinite uncertainty in the position (which is why it is then distributed across the whole universe), but this is an impossibility by Heisenberg's principle, which states there is a minimum amount of combined uncertainty.

This has been a great series, thank you for making it!

This is fantastic! Really amazing to get a proper explanation that bridges the gap between what we learn at uni and what we see in popular science content.

Favorite new nerd channel. Love to see it.

this is *such* a good explanation of what being a "quantum of light" actually means. thank you.

I really appreciate the summary of your understanding of light. That helped me consolidate what you taught us and left me feeling confident that I understand light a little better now.

Absolutely love your commitment to great explanations! thank you.

Regarding the hair experiment... I didn't notice a lot of "frizz" of your hair. Perhaps your hair has a protectant on it? Sometimes it can be a hair product, or perhaps the humidity at your location is preventing static build up? (Are you sure you are making a good static build up?)

Very enjoyable video! The statements about a photon's spatial extent are incorrect and I hope I can add some constructive feedback. A single photon state can absolutely exhibit a spatially/temporally short gaussian wave packet, and really can look just like the cartoon "wave packet photon". Think about using a femtosecond laser in a pump/probe experiment: the laser probes a transient chemical reaction (or whatever) during only an extremely short period of time. The video asserts that this type of confined temporal extent can only come from multiple photons (13:30). But what if we add neutral density filters in the femtosecond beam until only one photon per second on average comes through? Does the experiment still work, and still only probe the reaction during a brief time? Absolutely! Temporal extent and spectral width are complementary variables in QM (they embody longitudinal position and momentum of a photon), and Heisenberg's uncertainty principle tells us that a real (non-temporally-infinite) single photon state needs to occupy both limited temporal extend and some finite spectral extent. Every real single photon state effectively MUST have somewhat uncertain color! Interestingly, Fourier analysis theory tells us something similar about classical waves: a temporally short classical wave packet must also have increased spectral breadth. I think the confusing part is that QM is telling us that energy is discrete, and we are very familiar with spectrally narrow sources in physics experiments, and so we tend to think of these discrete energy packets as having one color (and correspondingly large temporally extent). But QM never said that: it just says that the energy is discrete, and once you add Heisenberg into the mix it's natural that we don't actually know the amount of energy (color) with perfect certainty. It's just as valid to apply QM to a temporally short wave packet, to say that there are multiple photons' worth of energy contained in it, and to say that it necessarily doesn't have a single color. We just lose certainty about the exact energy of a photon (and maybe also certainty about the photon number? unsure on that one, but "squeezed light" is a very interesting thing to read about, and in particular the tortuous things which the LIGO collaboration are doing to light for gravitational wave detection). There's another incorrect statement that needs to be addressed about plane waves (around 20:00). This is the second video in which this statement was made: something to the effect that a plane wave can only correspond to a photon of infinite temporal duration. Here, we're conflating transverse momentum and longitudinal momentum. The complementarity principle is a bit weird in this case. While the longitudinal momentum uncertainty (which is what we called spectral width above) is complementary with longitudinal position uncertainty (what we meant above when we talked about temporal extent), the transverse momentum (or beam direction) is complementary with the transverse position (or beam width). This particular complementarity actually doesn't differ between classical and quantum mechanics, QM doesn't actually have anything to add on this point. A plane wave is a photon state (or classical wave) whose direction is perfectly known, but whose transverse position is completely unknown: it's a beam that's infinitely WIDE, not a beam of infinite duration. This is all lumped under the heading of beam diffraction. Anyway, hope this feedback is helpful, keep making these great videos and I'll keep enjoying them!

Great video as always. I can tell you put a buuuunch of work in what with all these art projects :) the electrons are adorable!

I really like this channel. She explains things well and shows your examples without just spitting out a bunch of words I'm suppose to believe by showing pictures or diagrams drawn by someone else or a computer.

It looked like the room was lighted with essentially white light. There will be some blue which may cause the electrons to simply go away. Try again in the dark or under a darkroom light (red).

Lovely presentation!

I really appreciate the clarity and enthusiasm you have put in this video. Your description of the detector provides the same explanation of why the Hanbury-Brown and Twiss experiment works, which is the way in which we test for a single photon source in the lab! Very very cool video

That was a great explanation of how the photoelectric effect works! Thanks so much.

The way I finally started thinking about it is that light is a wave, but when it interacts with something it doesn’t interact along the whole wave. All the energy contained in the wave gets “zapped” down to a single point. It may not be completely factually correct but it makes the whole wave-particle duality seem less weird and mysterious to me. It really starts to get trippy when you think about matter interacting the same way on a quantum level.

I know that single-particle states are usually defined as momentum eigenstates, but iirc you can have single-particle states that are smeared across different momenta with varying amplitudes such that you have, for example, a single-particle state with definite position.

This truly an award winning video. You are allowing other scienctific experts like myself (Chem PhD) to get insights into physics we did not have. We "know" how to use the photon concepts to understand our experiments. But this is truly understanding "near reality" model stuff. Thank you!

This Video is so greate, explaines the photo electric effect experiment very well. Good job, pls more of it! 👍👍

Although the photoelectric effect proved the classical EM model was flawed, it did NOT prove that light travels as a particle. It proved only that when light is absorbed, a quantum of its energy is absorbed (converted into potential energy, and typically some kinetic energy, of the electron that absorbed it). It should have been immediately obvious to Einstein and other physicists that the photoelectric effect does NOT imply the light TRAVELS as a particle, BEFORE its energy is absorbed. Unfortunately, they had mental baggage -- what we now call the Locality assumption ("under no circumstances can mass or energy travel to a region of spacetime outside its future lightcone," which is still a very popular assumption) -- which led them to reject the otherwise reasonable idea that the quantum of energy may have been widely distributed in space a moment before the quantum of energy is entirely absorbed at a small location (the location of the electron). The Compton Scattering effect was similarly misinterpreted. It falsified the "classical" wave model of light, but it didn't really falsify the possibility that light is a "nonclassical" wave that has the quantum absorption property. It's a false dichotomy to believe the only alternative to the "classical wave" model is a "quantum particle" model. Looking Glass Universe posted a video about 2 years ago that claimed to provide a theoretical proof that light cannot travel as a wave. That proof depended on the Locality assumption: that if the energy of the wave is widely distributed a moment before the absorption event, then the energy cannot be entirely absorbed instantaneously (or nearly instantaneously) at a small location. The video didn't mention that Locality is only an assumption, and that Locality has been undermined by Bell's Theorem and experimental confirmation that entanglement violates Bell's Inequality. (Note: By "undermined" I don't mean falsified. I mean physicists have a stronger reason to doubt the assumption than they used to have.) I posted a comment to that old LGU video, about its dependence on the (unproven) Locality assumption. It's nice to see that LGU's thinking has evolved from that video's "travels as a particle" model to this new video's "actually travels as a wave, but absorbed like a particle" model. I hope a future video will revisit the old video's "proof," discuss its assumption of Locality, and discuss physics consequences of absorption's strong violation of Locality in the "nonclassical wave" model. For example, does absorption nonlocality violate the "No FTL Signaling" theorem? My intuition is that it doesn't... which ought to partially mollify Einstein.

Holy cow this makes so much more sense than the usual 'mind boggling' explanations and graphics we all see everywhere. So then, could it be argued that, if the photon is only detectable from an electron interaction, that light itself maybe isn't necessarily quantised, and instead it's the energy required to pop electrons that is?

This is the view that I always had (after doing my physics degree). I found your way very didatic. I always talked about modes. I also strugled with the mesurement. This makes lots of sense. Thank you!

What you do is truly inspiring! Explaining all that too, but that is not what I meant. But failing to recreate the experiment, not giving up, still making the video. That! You have courage and you didn't give up. You still made an amazing video! 💚

There seems to be some confusion here. Nothing in the video requires "particle"-like nature of light. This is well explained in semi-classical picture. Please don't mistake me for saying light don't act like particle at all, it's just it isn't the case here. 1) Photo-electric effect DO NOT need the "particle"-like behavior of light (more precisely and technically, EM wave to quantize) - the approach where you require the electrons to follow Schrodinger equation and study the interactions with EM field WITHOUT quantizing it, is called semi-classical model. It covers the photoelectric effect. 2) Reducing energy below "h nu" is not enough - way below one photon energy, EM waves still acts like just classical wave. Fully explainable using semi-classical model. 3) Single photon source was first created by John Clauser in 1974 ("Experimental distinction between the quantum and classical field-theoretic predictions for the photoelectric effect". Phys. Rev. D. 9 (4): 853-860.) using cascade transition of mercury atom. Which, arguably, resulted in the Nobel Prize 2022, jointly with Alain Aspect and Anton Zeilinger, who beyond any doubt showed that quantization of light was needed. That is, it is possible to prepare an EM field state which acts in a way which is NOT accounted in semi-classical model and requires fully quantum treatment of EM field. 4) It's pretty hard to prepare single photon state and equally hard, if not more, to establish non-classical nature of such a state (basically, what Clauser-Aspect-Zeilinger did was no small feat) - One way to establish non-classical nature of such a state is photon anti-bunching. Note, very low energy light (even a minuscule fraction of "h nu") still DO NOT generally exhibit anti-bunching BUT single photon source (single photon fock state) do. 5) If you are wondering, ultraviolet catastrophe and discrete spectrum of atoms like hydrogen also DO NOT requires EM field quantization, that is, DO NOT require "particle"-like nature of light, just the quantum mechanics of electrons with usual classical light already covers all these.

This is really cool. But I must say I am even more confused than before, when I was blissfully ignorant on problems of reconciling the interpretations of classical and quantum electrodynamics. * One claim is that a single monochromatic photon is given by a plane wave, and thus does not have a position at all, as it is literally everywhere. Since that is not possible, you state that a single photon is a theoretical approximation that does not happen in reality. So what does happen in reality then? What are the fundamental building blocks of light in reality, if they are not photons? * I remember that for wave packets it was always instructive to look at water waves, as they exhibit exactly the same properties as electrodynamic and quantum waves, including Heisenberg's Uncertainty Principle. A wave on the surface of the sea can be decomposed into imaginary Fourier harmonics either in position-space, or velocity space. Each harmonic either has a fixed velocity and an undefined position, or vice-versa. Waves have a gaussian distribution of positions and velocities, and the relations between widths of those is given by a relation very similar to the uncertainty principle in QM. However, the interpretation here is rather simple. A water wave is a collective effect of a large amount of basic objects. These objects have different locations and have different velocities. One can attempt to define a single velocity or a single position for the collective object we call a water wave. What the uncertainty relations tell us is that any such definition will be more or less meaningful depending on how spread out the wave is in position or velocity space. Most importantly, the water wave has fundamental building blocks - the atoms of water, that oscillate in space, and thus the wave emerges from their collective behaviour. This is yet another reason why theories that prescribe wave-like behaviour to its building blocks make no sense to me. If waves are composite effects, how can a basic building block of a theory be a wave or behave like one?

Thanks a lot, amazing video as the ones before. I'm so happy I accidentally bumped into your channel!

What an excellent video! I have seen that Gaussian wave packet illustration in so many contexts that I thought that's how light 'really' was like. This completely changed my mind.

It's great to hear the shout-out for Huygens Optics, I've enjoyed his channel immensely as well as yours! A collab between you two would be a dream to watch. The one thing I'm left wondering, having watched your video now, is how _time_ figures into the understanding of what a photon is and isn't. If an idealised laser creates single-wavelength light, and the wave coming out of it is infinite in space, then the photons exist along the whole path the light is moving along, and are thus not bound in space along the direction of travel. But you turn the laser _on_ at some point, and you turn it _off_ at some point, and if your laser is blue, then it might cause a photo-electric effect in whatever you are pointing it at. If you keep this blue laser running for a while, this photo-electric effect is pushing off electron after electron. Clearly this means there must be several wave-function collapses, and thus several photons in quick succession. How are the photons delineated in time?

For a single photon of light travelling (at c) across a distance, there is a time t0 when the intensity amplitude is zero (before the photon), a time t1 when the peak intensity amplitude is reached, and a time t2 when the intensity amplitude has returned to zero (end of photon). It is not the continuous (from the beginning of time until the end?) sinusoidal amplitude vs time function you showed. I think another confusion people have with these diagrams is they assume the x and y axis describe dimensions of space (ofc. the time axis is related to distance, but the intensity axis is not an indication of perpendicular movement)

Thank you once again for these videos, I learn a lot and they make me think.

This is new to me. I know the double slit experiments, partical wave duality etc but they have never made sense before. I think you've managed to present things that celebrity physicists gloss over. Well done.

Well done! A gentle and encouraging constructive criticism from a fellow physicist: it sounded to me (around 1:20) as if you were promising to explain the mechanism of wavefunction collapse. Of course, this is something nobody understands yet: we don't know what happens to go from a wavefunction to a discrete measurement. But I love your perspective, I love that you're sharing your playful, curious and humble learner's eye, and I love that you do the experiments. You earned a sub from me, and I'm excited to see more!

Not sure how to agree your proposition with a situation like this: imagine an atom in excited state which after some times relaxes by emitting light - supposedly a photon? It surely can't be plane wave and probably not even monochromatic but we usually call this a single photon. Should we then think that this type of emitted wave is some kind of special photon with special shape and so on who can be found in kinda random places with distribution given by the amplitude of calculated wave? I know I mix here a bit of a quantum and classical picture but I feel similar about what you have said so I hope this makes a sense to you.

I’m building a Flight Radio communications / navigation course and have been watching videos like this to understand electromagnetic energy. I know that a simplified explanation of these concepts would suffice for the level that I’m teaching, but I can’t help but try to understand fully what is happening. This has brought me to your videos. It started with trying to understand refraction because all of the explanations seem to contradict themselves. Now I’m here and I can’t stop. I really appreciate the effort you put into these videos. I feel like we are alike in that we seek to fully understand things and it will drive us crazy until we see it with our own eyes.

For the longest time, I’ve had more questions about the setup of the double slit experiment than the results themselves. This video and the Huygens optics callout do a fantastic job of explaining the experiment that the theories are based on. To me this also answers some questions on pilot wave theory.

You're not being very clear about what you mean by the energy in a classical wave. Energy in what? One wavelength worth? One second worth? In classical EM you can really only talk about energy densities. And the energy _per time_ passing through some region will depend on the wavelength _and_ the amplitude. For a given amplitude and a given time green light will still deliver more energy than red light. In QM we have an inherent energy density formulation of energy per frequency=h. I think there are really two main things we can talk about as "photons". A ground state excitation, which is generally not physical. Or a single wave packet. But you talk about these wave packets as if they're made of many photons. They're not. There is only one photon worth of energy in there. The wave packet arises from a time/energy uncertainty. If this wave packet interacts and deposits one photon worth of energy(which, as you mentioned, _can have different values_ ) it will be gone. Consider what happens when an electron falls into a lower energy state and gives off electromagnetic radiation. The energy is quantized. It isn't infinitely spread out. Is this a photon? I don't think that, when you lower the amplitude of your wave you don't deterministically have to wait longer for a photon. That is again mixing classical views with QM. You lower the probability of getting a photon quickly. You, and Huygensoptics, seem to argue that there is no quantization in the EM field, but only in the interactions with electrons. I don't think that is a tenable position after photon correlation experiments starting from the 70s.

Good morning from the USA! I always enjoy your videos. 👍👍

Great explanation at the end of the video about what light appears to be… it’s a wave but interacts with matter like a particle. Keep up the good work!

Possibly the calcium had an impure surface might have worked has you cut the surface layer off with a scalpel blade.

Hi dear, I have dsc in math and currently doing my thesis in quantum physics as well. Just want to say that these videos are very valuables and much more important than many people might think. In the modern world people have less and less understanding about the worldview, new logic system etc. that could however answer couple of questions (on the logical principles level). So keep up, you are loveable, nice and somebody who attracts positive attention. ❤❤ (and I have a crush on you) Good luck, Mithuna😊

this is actually a super well put out video, thanks a lot for not just repeat what everyone says a bout quantum mechanics :D

After years of quantum studies, this is by far the best extensive, yet enjoyable to digest series I've run across

i'm loving the endless crackpot commenters on this vid lol

This was a really excellent video. Keep trying with the experiments.

Another fantastic video! Thank you!

Thank you, I have spent over 30 years first exploring Astro Physics then Quantum Physics, this was very interesting, I look forward to viewing your catalog. Again thank you for sharing your knowledge

A lot in here I didn't know. Well explained - thank you!

This amazing video made a breakthrough in helping me understand the nature of photons. Everyone who is curious about physics should watch this video.

Wonderful explainer on the photoelectric effect.

This is an amazing video more for the failed attempts than the successful explanations: the reason is that very rarely do we get to see the “work” behind an experiment and the many unintuitive ways they can fail. Also, please don’t stop making experiments because they are the key to understanding. When they work you suddenly realise why they previously didn’t and gain a ton of knowledge as a result.

I grew up listening to science communicators. Unfortunately most fall into the poorly spoken , Sagan wannabes. So everytime your channel uploads, im always excited. Your delivery and matter of fact style is refreshing.

Very good video. It’s nice to hear someone ask questions that might not always “make sense” if you know the theory.

Such an awesome video. Thank you! 👍🏻

That was a fantastic explaination. Thank you

I'm gonna be honest. I did watch a lot of scientific videos before (less now), but I still watch your channel from time to time because of how refreshing and charming I think you are.

I love your videos but 4 years ago KZfaq stopped suggesting them to me and eventually i forgot to keep checking. Today all of a sudden your videos are back, now i know what i will do in the next days! PS: maybe if you dye your hair purple the experiment will work :)

Hey. That was a super informative video. Thanks for that.

3:19 that’s the best experiment video of all the internet! 😂 Funny, sweet and informative. Thank you!

Thank you for your explanation. Always wondered how a point-like photon particle emitted from a distant star is supposed to have no size but could potentially be observed at places that are light years away from each other.

Thank you for this. I didn't really get everything, but now I thoroughly know the difference between amplitude and wavelength.

Learned a lot, thanks, you are able to explain with such a clarity! I got distracted by your astonishing beauty and magnetism and had to rewind sometimes tough. 😅

I've watched many videos about light in my time. This one made me think a bit differently about it. Thanks!

Outstanding fashion to facilitate complex subjects to comprehend. You r gifted.....carry on.......Prof. Hassane Saadeh

Wow. You just explained something that has puzzled me for years. Threshold energy of photons in integers of a single photon relative to its wavelength. Now, _that_ I can completely picture in my head. Thanks!

Thank you so much for enlightening us. Got my sub.

You explained the wave function “collapse” without ever referring to the word “wave function collapse”. Very well done video!

Thanks for this enlightening video. It's been nearly 40 years since I studied high school physics, and I've only just realised that photons don't fly through the air in discrete packages of energy, but rather it's just that the electrons absorb finite units of energy from the light (obviously equivalent to the atomic orbital binding energy). I also loved the slit experiment explanation. That makes more sense now too.

Thank you for this video! Some stuff that I wasn't understanding really clicked. Could hit the Subscribe button fast enough.

THANK YOU! I've been wondering about discreteness vs light for a while now (I'm just a curious lay person). In particular, I was confused about how if photos of only certain wavelengths can exist what about redshift will seem to be continous, not discrete? You answered that and more for me. As for the interactions itself I've always thought that it wasn't that unreasonable for something that is a wave to have a point where it interacts, even though it is still a wave. I guess the missing piece was the time element that you so elequently explained in this video. So thank you so much! Absolutely the best video I've seen on light ever!

In the double slit experiment, I always thought light was like a wave of water passing through the slits and simultaneously hitting the wall in the end. But in fact each photon ultimately collapses to a single point on the wall individually - the wave is just the probabilities of its ultimate location that interferes with itself. If we could observe individual photons in slow motion, we'd see them appearing as distinct, separate points within the interference pattern, each blinking into existence at different locations one after another. Your conclusion at the end was great! I did not fully understand every aspect of the video, but still feel like I took a much better understanding of light and photons out of it. Thank you :)

You are amazing girl! ♥

Wow!! You’ve just messed up my mind about what’s really a photon and what all this entails. I’m gonna have to watch this video a few more times to grasp all you said. 👏👏👏 Good job!! Thank you very much! 👍👍

Great videos, thank you for being so open about your doubts and questions. It's essential for true learning and science! 18:35 very unlikely, but not impossible. If you focus a very strong source you can get a very small area where 2 photon absorption happens and you can make a microscope on this principle (TPEF).

Your setup looks great

MITHUNA INCREASING THE PRODUCTION QUALITY EVERY VIDEO LETS GOOOOOOO

Intelligent, Beautiful, and Wise. I'm tuned in 💪🏼

awesome as always

A very refreshing angle to look at wave particle duality. You may be right

You're so good at explaining. "Admitting" to failed experiments just increases your credibility. 😶‍🌫️

Great video. Aroud 20:00 when you are talking about "isolating" one photon by minimizing amplitude, I think you've hit on a very cool example of the heisenberg uncertainty principle vis-a-vis energy and time

this video blew my mind!

Now you are starting to talk my language ay around 19:00. I new the physics leading up to here, but this is where I'm applying some research as we look at data signal transmission and detection through long lengths of fiber optic cable and why when we get to very high speeds we need to move to coherent optics in like a QAM=256 or higher constellation to be able to get the cleanest signal possible. The loss and scattering in the fiber along with the detector S/N sensitivity and that detection cycling capability is really important. I would rather live in the land of optical physics then in the mathematical probability world of Foward Error Correction algorithms and digital to analog conversions. I appreciate your analogies and animations.

I too got mesmerized by your beauty 😍

Your explanation of the photoelectric effect really makes it sound like the quantization occurs in the effect itself as the electron is ejected, rather than it being a property of light waves themselves. It’s like you’re slowly adding energy to all the electrons at once, but when one gets ejected, it abruptly uses all the energy that was adding up to do it and the others have to start over. What is a photon? It’s the energy required to eject an electron.

I really really appreciate your videos. They really make me think. This one I'm gonna be thinking about for some time, I think. As I listened, some questions came up in my mind that I'd like to throw out. Special relativity says that as something we are observing approaches the speed of light relative to us, it's length in the direction of travel as measured by us contracts. Something I've never gotten clear on about that is whether the space between the observer and the object, as measured by the observer, also contracts. I would think that it must, because the object could conceivably extend all the way from the observer to a distant point. If the object length contracts, then so does the distance to the distant point. Given that, it would seem that from the point of view of the photon, the size of the universe in the direction of photon travel should be zero. So then it would make sense that the photon itself would extend all the way across the universe. But consider a pulse of light traveling towards us from a distance star. It has a location, does it not? But this is saying that the photon can be localized in space, and does not extend indefinitely in the direction of travel, or even extend considerably in that direction. Confusing. In the experiment you described with photons shining on an array of pixel detectors, it seems to me that one has to know the size of the photon beam in order to know that it's shining on the array. That's a way in which the size of the photon must be known rather precisely. Confusing. We talk all the time about the frequency of light or conversely, it's wavelength. But if we know the wavelength of light precisely, that's kind of equivalent to knowing the position precisely, or it means we know something related to the position very precisely. This seems at odds with quantum mechanics. I really liked what you said at the end about different frequencies of photons arising out of an experiment involving a single photon frequency. It seems to me we really don't understand this stuff yet. From your description of photons, it sounds almost like the thing that quantizes a photon is the fact that an electron can only accept a quantized amount of energy from it. Or anything else, for that matter. But is that evidence that the photon is quantized, or is it evidence that exchange of energy is quantized?

Thank you for clearing this up, the "photon", "particle" story was confusing me too.