When I first started researching this I was just as confused by this as many of you, and believed he side-stepped the main question, but in fact he did answer it, we just couldn't accept the answer: Basically the 'canceled out' light isn't really 'canceled out' in the 1 + (-1) kind of sense, it's their PROBABILITY that cancels. I.e. basically the light goes somewhere else, somewhere it was less likely to go prior to the interference. Think of it like having two hallways, one is less desirable for some reason (let's say it's longer), so you PROBABLY take the other hallway. HOWEVER let's say this hallway gets crowded, now all of a sudden you take the other hallway despite it being less desirable. This is what the light is doing. Generally the majority of the light will shine on the screen, but due to the canceling probability spaces (wavelengths) all of a sudden the probability of them reflecting back into the machine becomes the most probable path.
Answer to the last question: When light is reflected at an optically denser medium (glass) when coming from an optically less denser medium (air) it gets phase shifted by pi/2. Now track the two light paths, and you will see they differ by exactly one phase shift of pi/2. That means if one interefers constructive, the other will do the opposite
Indeed. The two paths looks identical, but they are not! They are symmetrical (as you wrote). And to answer the question in the title - where does the light go? - one may follow its energy: skullsinthestars.com/2010/04/07/wave-interference-where-does-the-energy-go/
This is my attempt at the answer to his question at the end: the beam splitter has a thickness, assuming that it is a half-silvered mirror I imagine it could have a layer of silver nitrate around 200nm thick. the light that is returned to the source actually has a different arm length difference than the other since the light returning to the source has one half that was transmitted twice and the other is reflected twice giving a difference between the two lengths a difference of the thickness of the layer of silver.
Possible explanation: Remember that when a beam is internally reflected in a material it gets an additional phase difference of Pi. What I mean by internal reflection of a beam is a light ray that travels inside the material and in the interface glass- air gets reflected. One of the beams that gets reflected back to the source is reflected internally in the glass and so if the two beams that interfere in the Mickelson had initially a path difference of a factor of a wavelength (phase difference of 2nPi) producing a completely constructive interference, the beam that gets back to the source will have and additional half-wavelength path difference (due to that Pi additional phase difference caused by internal reflection) which will produce completely destructive interference.
Sort of correct. Except (1) It's not internal reflection; the beam-splitter has a dielectric or metal coating on one surface, where the reflection takes place. (2) The phase change occurs when light coming through air is reflected by the coating at the front surface. When the light comes through glass and is reflected by the coating (at the back surface) there is no phase change.
What I find more interesting after a second look at this is the number of rings that can be found by moving the mirror back one half the length of the laser chamber. My question is how far back would you have to move the laser back to double the number of waves.
I think you're misunderstanding what the rings are (or, I am). I believe the rings are visual representations of the frequency itself, meaning that the number of rings is neither increasing nor decreasing, but you're just seeing them in different positions. Think of those squishy toys that funnel in on themselves, or think of it like a single string vibrating. We're seeing the same vibration at different intervals of "time", which in this case is represented by distance.
@@holdmeclosertonydanza22 Red, should be a 650nm laser. So, when we are using rings or lines, we can count one ring going from light to dark to light again as a movement of 650nm. However, the laser chamber isn't exactly parallel, it is a rectangle. That gives the edges of the laser a different distance from corner to corner or in this case from center outward. I am of the opinion that there is a formula for laser diameter, chamber length, and ratio of the length of the two outside mirrors.
Interestingly, conservation of energy means that any " disturbance, change of state " in the universe must go somewhere, it cannot be destroyed. It appears to diminish something else must be absorbing that disturbance. It is a relay race that never ends. Therefore, if this is the case the disturbance itself must have received its energy from a previous disturbance. The question is where did the original disturbance come from where the Law does not apply?
When charge oscillates EM waves emerge from space. During total destructive interference EM waves oscillating in opposite direction cancel each other & dissipate back into space. EM waves are made of Space itself.
Where does the light go? Into the constructively interfered segment of the wave....that's why the constructive fringes are brighter than the un-interfered beam, right? It looks dark where we look into a dark fringe and it looks extra bright when we look into a constructive fringe......what am I missing here, why the mystery?
What if we use cubic beam splitter (that does not add the extra 180 degree phase shift) and have a phase difference of 180 degree between both arm lengths (to and fro)? Shouldn't that have a destructive interference everywhere (assuming perfect alignment)?
Me too - I'm getting sick up to the back teeth of experts DUCKING OUT to leave US with yet another puzzle when they haven't really answered the first question properly - This guy could sent a glass eye to sleep
I could be dead wrong, but if the reflected light (going back into the source) is 180 degrees out of for the direct beam, but not for the beam that gets reflected at the half-silvered mirror as that has to reflect twice on the less dense mirror, and once off of the full mirror. When one of the 2 waves is shifted 180 degrees it results in the constructive interference. In contrast, the original path has an equal number of reflective phase shifts, but the distance traveled is 1.5 times longer in one direction vs the other, such that the wavelength is offset but 180 degrees. Not a physics student so I might be missing some obvious thing here.
I pulled out some lens polarizers and did some experimenting. I think the answer to the puzzle in the setup is that where there are an odd number of mirror reflections between light of the same initial polarity, there will be destructive interference. Each successive mirror changes the polarity of light. If it reflects off one mirror it is now in the opposite phase, when it reflects of a second mirror it is now back in phase. Also convex lenses do not change phase. And the Professor also added a polarizer after the first mirror after the addition of the beam splitter for the returning light.
Actually, you'll have to read my post and click the wiki link, or look it up on beam splitters... normal mirrors are not phase shifting... But, a splitter 'can' be, but for only one surface, or multiple surfaces depending upon what kind is made.
Because it is not destructive interference. Neither matter nor energy can be destroyed. The first half mirror is working like a switch, with the wave pattern of one beam sending the laser to the detector or back to the laser depending on full or half frequency.
There is no such thing as fully destructive interference. The lesson to take from this video is that destructive interference in one location means there is constructive interference somewhere else. In the same way, constructive interference in one location means that there must be destructive interference somewhere else. The total amount of energy in any wave (light, water, sound, etc.) is always the same. Interference means moving the energy from one place to another.
Imagine two people and a rope. What happens is the waves with opposite phase meet at the center point which is not moved at all (destructive interference happens here), BUT the waves will continue travelling and then hit each person with same power as when sent, only the returning wave will have opposite phase then when sent. No energy lost.
@@LiborTinka Interestingly, conservation of energy means that any " disturbance, change of state " in the universe must go somewhere, it cannot be destroyed. It appears to diminish something else must be absorbing that disturbance. It is a relay race that never ends. Therefore, if this is the case the disturbance itself must have received its energy from a previous disturbance. The question is where did the original disturbance come from where the Law does not apply?
@@JohnnyAdroit The confusing aspect of this, is if you have two sinusoidal waves of equal frequency, but phase shifted by pi... Where then would the energy of the waves "go"? Does this effect hold up in 2D?
@@bermchasin If you create/draw a setup (using mirrors and beam splitters) where two beams of light are made to overlap with a phase difference of pi, you will find that the must be at least one other path out of the setup where the interference is not destructive. Try drawing a bunch of systems to get laser beams to overlap. Make sure to keep track of the distances traveled and the phase changes induced by the optical devices. Reflecting off a mirror or beam splitter causes a phase change of pi, passing through a beam splitter does nothing.
Lasing is a quantum mechanical phenomenon , depending on reflections to sustain the lasing action within the laser. The the whole system, optical bench-laser-cavity "lases". The reflected photons are a part of the coherent lasing action and the energy is part of the energy that exists within the lazing volume, just extended in space by mirrors and reflections. This is seen in the last demonstrations with the two beams . There always exists a return beam, except in total constructive . The solution to the last question of the overlap of the return with the forward wave ,when electromagnetic waves are considered to emerge from an ensemble of photons: There exists a very small probability of photon photon interactions , of order 10^-16 if the coupling constants in the loops are counted. It is the same reason that to see the interference pattern one needs material; the photons have a large probability to interact with the electrons in the material.
There is no such thing as photons. All the experiments show lights is waves, never particles. If light is particles, explain where are the particles which have been discarded by destructive interference. The alleged light particles have no charge so they can't mutually annihilate, so they must be laying around waiting for someone to sweep them up and put them in the trash.
@@dreamdiction see this simple experiment where single photons build up the classical double slit interference pattern www.sps.ch/artikel/progresses/wave-particle-duality-of-light-for-the-classroom-13/
@@annavayaki1735 You have obviously never done the experiment yourself so you believe whatever you are told to believe. What you mistakenly call "single photons" is a high frequency interrupter relay transmitter switch used to produce single separate individual wavelengths, like this ~ ~ ~ ~ ~ not "photon particles". Continuous waves produce interference patters, intermittent separate single waves also produce interference but at a slower rate/intensity because of the gaps between waves. The interference is the proof that light is waves at all frequencies, never particles. "Probability waves" only exist in researchers imagination, that's why nobody (including Broglie) could design an experiment which shows light is particles. The photoelectric effect is easily explained by blue light having the right frequency of positive/negative magnetic induction (alternating push/pull) to magnetically agitate a negatively charged election out of it's shell orbit, that's why the photoelectric effect does not work at higher or lower frequencies - nothing to do with "particles". Did you believe red light was waves but blue light magically manifested 'particles' which disappeared again at higher frequencies. Electromagnetic Radiation (EMR) is waves at all frequencies, all the experiments show light is waves, there is no experiment which shows light is 'particles'.
@@dreamdiction I am a retired physicist, having worked for 40 years in high energy physics experiments, from bubble chambers to the latest large detectors at CERN. Dream on your science fiction.
Enter the layman;--If the act of observation collapses the wave function, then does that not illustrate that there is more than one observer, and that the primary observer has the ability to change the rules of physics at will. Or does it illustrate that these rules are only rules because the primary observer creates the rules?
Where does the energy go? I thought I’d make a detailed explanation, for those unable to follow the simple correct answers given before mine. First, we have to make an assumption about the splitters, are they arraigned with the silver and glass sides oriented in the same direction, or is there a phase shift from one or both splitters due to the orientation. The phase depends upon our knowing what kind of splitter he is using. He doesn't say. Read here for detailed explanation: en.wikipedia.org/wiki/Beam_splitter Initially, we set up the Michelson Interferometer to display a bright spot at the center of a display to create an interference beam which is constructive along the center which alternates from bright to dark every λ/2 (half wave) (length?) change in the angle. Each Δ of λ/4 in the adjustment arm creates a ΔL of 2* λ/4 or a λ/2 (180°) phase shift. The splitters ‘usually’ used in these experiments have a phase shifting side, and 3 non-phase shifting directions, just so you can play with effects like we see here. It’s a great test of one’s understanding of the phenomena! This is MIT, who knows; but, it does make a difference, and he does seem to have a 'smirk' in his smile. :-/ I suspect… subtlety! ;-) To understand, one must know ‘precisely’ the processes going on here. This kind of experiment sets MIT apart from smaller colleges and universities. One, for the uninformed, it is a real challenge. Two, for the savvy student, it challenges conceived notions and requires one to examine testing procedures at the level required to make quality experimentation. Imagine if this were to be published as a paper!? How foolish would we feel? This is a great example of the kind of critical and divergent thinking needed today. In most cases, the primary and principle design and purpose of the Michelson interferometer is solely to show an interference pattern, a second splitter does not get used. As a simple interferometer, whether one leg is phase shifted does not matter. Note: When I refer to return path, I am referring to the actual return path which is the pass through path from the adjustment arm mirror, which when hitting the splitter on the return is both diverted to the left leg, phase shifted 180°, and passed through in a return path to the laser shifted 0°. However, in this set up, the paths are "not" the same in how we create the two interference patterns. Though he says they are, the return path beam, which he calls “the other arm” from the adjustment mirror, strikes the back side of the splitter when it makes the 90° turn into the mirror and lens and then on to the screen. The back of the screen introduces a phase shift of 180°. Since the adjusting mirror sets up the interference, this phase reversal has no effect, when using the interferometer as in the first half of the experiement. However, with the introduction of a second splitter, this 180° shift comes into play relative to the reference beam on the fixed leg, with the addition of the interference pattern created for the ‘return’ beam. It’s interesting to note that if the interference pattern of the first half did actually produce an inverted pattern traveling backwards through the beam, it would phase cancel the entire beam according to Quantum Mechanics, so no reflected beam, this is complex in understanding the fundamental concept behind “Where does the light go”. What kind of splitter is he using is crucial to our understanding. As an outsider student gleaning information and watching courses from MIT, Stanford, and all the others. I personally think it is a heinous crime to leave out such critical information; there are enough people out there who do not understand this process, and will not take this parameter into account. Someone suggested he would get into trouble if he stated where the light really went; in the case of current affairs he does cater to two schools of thought by removing this critical piece of information. When I first saw the video, I thought I was going to have to dump all my research! He could easily have thrown me by stating what kind of splitter this was, and were I to discover the splitter did not have a phase shifting back. The interference pattern through the return path does not use the reflecting side of the ‘first’ splitter for one of the legs creating the interference. (This is a critical point, and the whole experiment hinges on this information.) In this case, the ‘return’ legs are both at 0° relative to each other to create interference. This means that the two legs do take different paths than the first, to create the interference pattern for the “return” beam’s path. The return path, before it reaches the second splitter already exists as an interference pattern. The second splitter doesn't do anything but redirect the already existing interference pattern into the viewing leg. The second splitter, no matter what kind of splitter, does not change the relationship between the two beams already existing as the interference for the return leg because if silvered, the both beams are shifted by 180°, and if glass, both beams are not shifted and remain at 0°. Shifting the interference pattern by 180° does not affect the banding created! Shifting one leg or the other does and in this case, the second splitter has no effect on the interference created prior to reaching it. Note however, it does change the intensity, as each splitter divides the intensity by 50%, the amplitude is affected, but not the phase relationships of the pass through beam from the laser. To summarize, in the top path, one leg is at 0°, and the second leg is at 180°. In the return path, before it reaches the second splitter, one leg is at 0°, and the second leg is at 0°, therefore the interference pattern is inverted. If we set the first path to create a constructive interference at the center, the return path, not shifted by 180° is destructive; or vice versa, the first path creates a destructive center, and the return path, not shifted by 180° creates a constructive center. What is required to flip the orientation is to change “ONE” path by 180°, but not the other. In this case, the fixed leg of the interferometer is the reference point. He is incorrect when he says both paths are the same, unless he means the paths of the two legs reaching the splitter is the same. However for the top, the Adjustment leg is phase shifted for the top interference pattern on the screen, but the Adjustment leg is NOT phase shifted through the splitter for the bottom interference pattern, the return path, when displayed on the screen. The second splitter added later only serves to allow the initial reference beam to pass through (0°), and to redirect the return half of the beam into the second path. Again, since the interference pattern already exists before it reaches the second splitter, reflecting off of the second splitter either modifies both legs 180°, or it does not. Phase shifting the interfered beam by 180° does not change the interference pattern because both legs or beams creating the interference maintain their internal basis relative to one another. Of course, if the splitter does not have a phase shifting back of a silvered half, then he has proven Quantum Physics (or QM) false. This experiment examines the most fundamental principle of wave function, what happens during destructive interference; the concept that got me interested in Quantum Physics in the first place. Where does the energy go? Are all three vectors phase shifted by 180°, spin, electro and magnetic, or only one, or two? What, if anything, remains observable in reality, when destructive interference happens? If the energy cannot be observed, where is it? The answer can be found in 'complex eigenstates'.
No, because it is unobservable. That's the classical answer. If I might ask, exactly what phenomena are you looking for (I'm not sure); and what is your background? It's fairly well understood that destructive interference appears to create a 90° shift in the normal, and this is apparently a complex vector. However, in reality, matter interacts with matter, and if the matter interacting has things like electrons and nuclei which they do, then we might conjecture that they also consist of interference patterns which can interact constructively and destructively. For all we know in a double slit experiment, the light is interacting with the matter of the slit itself at the edges, and the electrons in the material of the edges are altering the phase of the emerging wave. Still the destructively interfered wave points appear at the constructive interference sites. This could be a complex vector reflection being reflected back again by electron interference of the reflecting surface material. [180° is destructive, creates 90° rotation, and at π/2 a surface electron reflects it back] and if that whole pattern is reflected and 180° out of phase with originating phase of incoming. Where does it go? A: 90° complex phase shift. Hypothesizing, of course, that matter is nothing more than a sum of constructive and destructive interference points. (Holographic Universe). I believe I have a mathematical model of an electron which explains 1/2 spin in terms of simple dimensional interference. (I believe in layman terms we can extrapolate this behavior cognitively by use of simple 2D moire patterns to show the relationship between the math and physical states of matter existing as fixed nodes, and radiating out from that as photons due to resonance.). The problem observationally is simply that the angular momentum of the electron is too fast to observe independant states. For all we know, the electron spends half of its time being unobservable and what we're seeing is the "fan" illusion, where something that appears solid, it really just the blades moving so fast you can't poke your finger between the blades. I feel strongly that we never see the full energy of an particle at any given time, no matter how we measure it. And saying half could be an understatement. We always square everything to get real roots, just to make it observable; that bothers me. It bothered Heisenberg, and Planck and classical convention and politics forced them to describe things differently than they wanted. I think Pauli was in on that too; I certainly agree. The subject was Quantizing angular momentum, and from that we still deal with probability. I've moved on to Bohmian Mechanics (BM), as from my personal research I think there's better evidence to support that theory, especially with recent entanglement experiments. All along I independently developed my own theory which I later discovered was a variant of the pilot wave theory and BM . The behavior I mentioned about the splitters and is well documented in the specifications of the various types of splitters. The rest is common sense and logics, binary logic in this case which keeps it simple. One need only keep track of the front or back of the splitter, and thus the type. So, on that note: original research of the mind I guess one could say. So, I'm not really sure which phenomenon you are referring. The experiment fascinated me, as I was hoping to learn something from it. Instead I found neither a confirmation or denial because of lack of information concerning the splitter specifications. So, a poor experiment, in my book, at least in terms of figuring out WIGO, vs WOSIGO, or What is going on vs What one sees is going on. I'm really just looking for information to prove or disprove my theories. All experiments in my research are mind experiments as I have no laboratory. I call it Phase Theory, not to be confused with the Wikipedia Phase Theory that's been around a while; but, I've focused on constructive and destructive interference. Science has spend a lot of time and experimentation and development of constructive interference (Phase conjugate mirrors, Star Wars Defense, Holographic Identification, Photon doubling, Atmospheric interference corrections in Astronomy to name a few), but makes little to no effort to examine the destructive interference effect, and that it appears to be a gateway into N-space dimensional interference, primarily because of the "Where does it go" phenomena, and that based on QM and BM the effect is usually complex, and thus defined as "unobservable" in QM terms as in some aspects of entanglement has shown, unmeasurable. Entanglement claims to disprove the local hidden variable theory; but, and I'm still absorbing BM, and my theory theorizes a possible local hidden variable which can't be accounted for in current experiments. But, it's an N-space problem, and not easily observable if at all, thus mind experiments. So, based on my key word usage, these are areas you can read about.
+David C. Huculak Wow! Thank you, a very nice post. I'm more used to internet Trolls that defend as if their life depended upon it, a 3D observable universe, and anything contrary to that concept, freaks out their little monkey brains. lol I learned about uncertainty, and quantum mechanics much later in life. I abhorred the probability approach until I understood it. It took much doing because everything I had come to understand didn't allow it; but, at that time I couldn't imagine wave function. I really became serious when I was 30 years old, I'm 61 now. I had read a book written by what many would still today call a goof ball, and paid little attention to him. I felt, if I were to learn to think out of the box, I had to destroy the box first. So, I never limited myself to solely classical studies; and I'm self taught all the way pretty much, that is except for college and university level math, physics and calculus. I am self taught in linear algebra, and with that the translational geometrical identities, rotation, translation, etc. Much needed to understand classical Quantum Mechanics. Heisenberg's uncertainty requires a mental image of wave function to see why it doesn't specifically conform to linear vectors, however the wave function follows basically a vector form, like a spiral around a vector. I realized anything I decided had to agree with anything we'd observed in physics to date. However, I also realized that it would only have to conform to observables, a term I later used and interchangeably with the term 'reality' and decided to call anything that was beyond observable geometry as existing, or saying instead of reality, existence even though it didn't specify to what level it exists, like a thought experiment. It's more complex than this; but, it suffices for the time. In the book I read, the "scientist" made one statement I pondered for several years. He stated that a photon was an electron rotated out of phase by 90°. Already familiar with both electrons, and their parametrics, and photons and their parametrics, I observed that they were very similar indeed, almost too similar, it seemed strange that they were so similar. In fact, at the time, the only difference I could see between the electron and photon was that one (the electron) had mass, and moved slow; and the other (the photon) was 'massless' and moved at the speed of light. Other than those two things, they were nearly identical. I didn't believe in coincidences, except maybe randomly. When I tried to discuss this with my professors, or other learned men, I was either way over their head, or they rejected me outright without thought, which confused me, as I was just making inquiry, not a statement of fact. That was 30+ years ago. My first hero was Einstein, and my second was Nikola Tesla. Through Einstein, I was interested in time and light, and through Nikola, I was interested in resonance; this led me to constructive and destructive interference which is present in photons. When I was 12, and I saw my first electromagnetic chart, my mind imagined that based on what I was seeing, matter must be at the very low end of the spectrum, and have a very long wavelength. Such is the naivete of a child. But, I never lost my curiosity as to whether everything was just part of the EM spectrum. I also noticed on a map of the globe, that all the pieces fit together somewhat like a jig saw puzzle. I thought this curious, and that was 1968 long before plate tectonics was known. But, that's another story; I'm interested in a lot of things. And I am one of those strange kind of people that just can suck up everything they read; although, my years are starting to show... to me. I am either unemployed right now; or, I am retired; not sure which being 61. But, because of an auto accident 10+ years ago; I'd definitely say I'm disabled as I received as a passenger really bad back injury which limits my present physical abilities, though one can hardly tell to look at me. But, it forced me to completely give up most physical activity, and I therefore only had my mind to work with. Thank goodness, I was interested in just about everything; but, loved physics, and philosophy, computers, etc. So, I consider my hobbies, my work, and right now "my" Phase Theory" and supporting activities take up most of my time, with some 'shiny object' distractions. I'm getting older; but, I'm currently studying python (a programming language) with the eye towards modifying Blender, a extremely sophisticated 3D drawing tool so that I could make n-space objects and the mathematics surrounding their behavior. The spreadsheet was much too limiting. I would give just about anything to have some people helping me; as I see it, unless we're all "changed in the twinkling of an eye" I'll run out of time before I develop FTL(sic) and matter teleportation; I think QM energy sources are on their way into the public as we speak, several if what I see emerging is what I think it is. I can even explain how they work, though the developers are a little hazy on theory; they're more like Tesla, a real hands on guy. My best skills are multi-dimensional spatialization, and an intuitive grasp of the math. I would love to find a like minded peer or two or more! So, no job; but, I do physics full time! :-) I believe the gateway to the greatness of the cosmos is in understanding the role of resonant coherent destructive phase cancellation. Controlled, of course XD. I hope this isn't too long. I could lecture, discuss or have discourse on these topics ad nauseam... not to me, of course ;-) I would love to specifically find someone who could show me where my thinking has gone awry! Or, in other words, where I'm wrong. I became interested in phase conjugation in 1980-81. My first 'aha' moment in Calculus *theory* occurred in 1981. Applied calculus was too mundane. Any suggestions, help, information, discussion, you name it, you could provide would be greatly appreciated. Thank you for asking! PS: I haven't played in a while; but, while I did, I loved playing Go! Unfortunately a lack of playing partners that could compete forced me to move on. It's been 20+ years since I played, fascinating game, so many permutations.
+Chip Cooper Can you at least provide figures for your explanation? some of your terms in your explanation are rather ambiguous, for like, "left leg", "back side of the splitter", "The back of the screen introduces a phase shift of 180 degree", "first splitter", "viewing leg". Can you at least unify the terms? Also, I'm not sure I understood "return path" from your definition, though I get grasp of it
Jeong Hoon hard to believe that I wrote that less than two months ago. Seems like ages. I don't exactly recall; but, I tried to use the terms he uses in the video when I could for consistency. From what I do recall, we have the interferometer, and the extras he added to make the return trip. I know when I refer to the back side of the splitter; I'm referring to the different types of splitters, and we don't know what type he's using here. But, splitters *can* have a mirrored side and a glass side. Without reviewing what I read, the back side of the splitter would have been referred in this case to either the one that does a phase change vs the side that doesn't cause a phase shift. I believe I set up which is which when I discuss different splitters. (This is just a quick response; I can't get into the test right now. I'm working one a spinor based n-space mathematical model of a 1/2 spin particle at the moment, purely theoretical, of course. So, let me copy your response and take some responses there from memory. +Chip Cooper Can you at least provide figures for your explanation? *I believe I used his set up as viewed from the front of the table, closest, the narrow side) some of your terms in your explanation are rather ambiguous, for like, "left leg" (probably the return leg he added later), "back side of the splitter" (explained earlier), "The back of the screen introduces a phase shift of 180 degree" (refers to the atomic and subatomic structure of the screen acting upon the interference pattern making the light visible), "first splitter" (the splitter first in path after emission from the laser), "viewing leg" (not sure, the leg to the screen).. Can you at least unify the terms? Also, I'm not sure I understood "return path" from your definition, though I get grasp of it If this isn't enough, write back using Google+ notifications, and you can tag me in there. UA-cam stopped allowing tags on the UA-cam video web page, and it's only active in Google Notifications window, like I did for you. I'll look again and re-read what I said, so I can clarify. As I recall, it took me some thinking to follow all the paths. I drew myself a diagram; but, don't know where the notes are, if it wasn't just an envelope. I've spent 30 years thinking about deconstructive interference. I think the term destructive is a misnomer, and that phase cancelling vectors are a well kept secret, or completely ignored subject area in physics little understood. Thus the question, where does it go. This has answers to the double slit experiment, if examined properly. However, keep in mind, we don't know what type splitter he used. Some don't have the 180° phase shift on one side, some do, it's a critical part of the critical thinking, as I'm sure you have or will realize. I don't know if as instructional, it was intentional or not, leaving the piece of data out of the video. It certainly hampers drawing a definitive conclusion. I apologize, but it would take me almost as long to redo this experiment, done mostly in my head, as I did before. I only need to write down where the beam was phase inverted, in a binary form. 0 for no shift, and 1 for inverted, the rest is logic and following all paths. I have been picking up a 3D drawing program Blender so that I could eventually draw these and create a video.for more complicated explanations. This might make a good first project for me as I've gained some skill since I wrote this post. Blender is written in Python, and I hope to familiarize myself with it, as I'd like to modify the drawing program to handle n-space vectors and spinors adding some controls to limit viewing areas to 3 orthogonal dimensional constraints. It's hard enough to imagine 3D on a 2D screen, fortunately as humans we're pretty good at that. However 6 or 9 dimensions, not so much. I have my weak areas, and I'm picking up missing information as quickly as possible; although I have been working on this abstractly for over 30 years.
+Chip Cooper Wow, your response is immediate! I wonder if I can send you privately? I want to send some diagrams I've drawn, and see if it makes sense, because in my diagram, both the interference at the screen and interference of beams to the source make constructive/destructive simultaneously!
One question... the effect that you get constructive interference at one output while you get destructive interference in the other output is due to the induced phase shift for one of the interferometer arms. So if you could take a beam splitter which does not induce any phase shift or symmetric phase shift for both arms, it should be able to eliminate the complete light... Right?
The answer to the last question is simple. When the two lights were interfering destructively, they already have an effective path difference of lamda/2. Now, in case of the light totally sent back to the source, an additional path difference of lamda/2 is introduced in one beam of light making the total path difference an even multiple of lamda which is the condition for constructive interference.
Which side of the center lens does light reflect off of. Does it always reflect off the front side or always the backside? (Front being the incident side) seems pretty important to answer the question
How is a beamsplitter actually made? Usually it is a piece of glass with a dielectric or metal coating on the front surface. Light striking it from the front has a 50% (or any other value, depending on the coating) chance of being reflected, and a 50% chance of being transmitted. In the case of a dielectric (non-conducting and non-magnetic) a reflection does indeed induce a phase shift of π, whereas a transmitted photon picks up no phase shift. Details: www.cs.princeton.edu/courses/archive/fall06/cos576/papers/zetie_et_al_mach_zehnder00.pdf More: What happens to a photon approaching the beamsplitter from behind? There it first enters the glass (ignoring the small chance of reflection off the air-glass interface) and has a 50% chance of reflecting off the dielectric coating whilst within the glass - this reflection does not induce a phase change.
Ok so noise canceling headphones use disruptive interference with sound. so why hasn't anyone used this same concept to build a real Light saber yet? Say you have 2 laser on exactly opposite frequencies pointed at the same point in space shouldn't they cancel each other out? Thus stopping both lasers at that point essentially creating a real light saber. Just wondering why no one has done this yet.
No one has done that, yet, because it's impossible. Interference is not an actual interaction. It can't and does not stop energy flow. We did show this to you in school with wave experiments, by the way. You were simply not picking up what we were trying to explain because it's not completely obvious. It escapes most students, including myself. I didn't understand this correctly until I took a math class in university years later.
Can anyone explain to me how the beam "knows" it's going to destructively interfere after traversing the beam splitter (i.e. meeting the other reflected light beam), so that it decides to reflect instead? To me this appears as if the light can "look" into the future, something like "Hey, it seems as if I am about to destructively interfere with another light source an inch ahead, therefor I must reflect off this surface instead of transverse it.".
If I understand your question, the thing is you are thinking light is interfering at the screen, while the destructive interference state is present right at the point they mix. No light departs from that point to the "destructive interf. arm".
Light can not create stable matter. It can, at most, create an electron-positron pair. Unless you have a way to safely discard that positron, your electron won't be around for too long, either.
Is this how the FBI and other spy agencies listen to terrorist planning terror acts as they point a laser beam (which doesn't have to be visible beam and can be infra red laser, such that window panes reflecting the beam gets modulated by sound waves and the spy agencies can listen to enemy, I could see as you were speaking the beam was modulating as well as when you pressed on the table.
I don't know that it's not possible. If waves cancel eachother out then the energy is destroyed. Is light just a packet of energy? If so then light can be destroyed through destructive interference.
That's because red light is ~ 800nm in wavelength and we need to shift a beam by 400nm , it's hard to make an object not move by that ammount, even sound vibrations would ruin the interference
Sleepyeyeguy;--The "law" of the conservation of energy says that nothing is ever destroyed. It is merely converted into matter, light, heat, or motion. So when the interference pattern shows that two waves of light interfere with each other, then that light must disappear somewhere,(or somewhen). Or, maybe we are now observing the first concrete evidence on Earth of "dark matter". It appears dark to us, but in a parallel universe, it becomes light.
The light vanishes from view but it does not reappear in another universe and it does not have anything to do with dark matter. Does the ocean vanish and reappear in another universe when its waves cancel out? You're just adding opposites. 1 plus -1 equals 0. Everything is conserved.
Ah but a photon only "appears" when it interacts with something. Hence when the waves cancel, the photons simply don't produce an interaction. What happens? They keep going where they're going!
If light is particles, explain where are the particles which have been discarded by destructive interference. The alleged light particles have no charge so they can't mutually annihilate, so they must be laying around waiting for someone to sweep them up and put them in the trash.
That's because he left out information. This is a part of an MIT course, and a problem... note the '?' question mark. Think of it as a voluntary quiz. Read other replies for the answer... some are right, some are wrong.
The questions in this experiment are legion, but the major one is this;--How much intelligence must an observer have to collapse the wave function? Can an insect, (or insects), collapse the wave function? How about a cat, or dog? If any observer, (no matter the species), observes the experiment at a later time, can they then collapse the wave function? These primary questions should not be obfuscated with math or creative scientific language by those who do not wish to reveal that they do not understand what is happening here, any more than we do.
No intelligence is required. A camera can collapse the wave function. You may sometimes hear of an "observer" collapsing a wave function, but really it is a measurement that collapses it. To try to explain it in un-obfuscated language; how much intelligence does it take to measure the width of a blade of grass? Its width is "unknown" until it's somehow measured. But an insect can "measure" the grass (by stepping on it and having a sense of its size), as can a human, as can a totall intelligence-less camera (by taking a picture and knowing how far away the grass is).
No, it's true! It's about frames of reference. "Collapsing the wave function" is not a universal concept, it occurs only within a given frame of reference. A frame of reference does not require "intelligence" or "consciousness." The camera's frame of reference is different from yours. When the camera observes the grass (or whatever), the measurement is done from its frame of reference. When you observe the camera's results, the measurement is then done from YOUR frame of reference. Get it?
The light does not go anywhere . Light does not imit anything . It's like everything you've ever known including the earth and the sun and the moon is flowing through a river a continuous river . And when you drop something say a rock in the river it forms an attraction current like an eddy . Light is the same . Everything is The light .
Instead of solving a problem, leave us with a riddle. Thanks. Video must be very old since a light pen would have worked. Looked like he had part of cern on the table. LOL
When I first started researching this I was just as confused by this as many of you, and believed he side-stepped the main question, but in fact he did answer it, we just couldn't accept the answer:
Basically the 'canceled out' light isn't really 'canceled out' in the 1 + (-1) kind of sense, it's their PROBABILITY that cancels. I.e. basically the light goes somewhere else, somewhere it was less likely to go prior to the interference.
Think of it like having two hallways, one is less desirable for some reason (let's say it's longer), so you PROBABLY take the other hallway. HOWEVER let's say this hallway gets crowded, now all of a sudden you take the other hallway despite it being less desirable. This is what the light is doing. Generally the majority of the light will shine on the screen, but due to the canceling probability spaces (wavelengths) all of a sudden the probability of them reflecting back into the machine becomes the most probable path.
thanks
@SaltyBrains It doesn't go anywhere. It forms a standing wave in the chamber. This is the principle of the laser (as you have correctly anticipated).
RIP Professor Ziggy Ezekiel.
Answer to the last question: When light is reflected at an optically denser medium (glass) when coming from an optically less denser medium (air) it gets phase shifted by pi/2. Now track the two light paths, and you will see they differ by exactly one phase shift of pi/2. That means if one interefers constructive, the other will do the opposite
Indeed. The two paths looks identical, but they are not! They are symmetrical (as you wrote). And to answer the question in the title - where does the light go? - one may follow its energy:
skullsinthestars.com/2010/04/07/wave-interference-where-does-the-energy-go/
This is my attempt at the answer to his question at the end: the beam splitter has a thickness, assuming that it is a half-silvered mirror I imagine it could have a layer of silver nitrate around 200nm thick. the light that is returned to the source actually has a different arm length difference than the other since the light returning to the source has one half that was transmitted twice and the other is reflected twice giving a difference between the two lengths a difference of the thickness of the layer of silver.
Possible explanation: Remember that when a beam is internally reflected in a material it gets an additional phase difference of Pi. What I mean by internal reflection of a beam is a light ray that travels inside the material and in the interface glass- air gets reflected. One of the beams that gets reflected back to the source is reflected internally in the glass and so if the two beams that interfere in the Mickelson had initially a path difference of a factor of a wavelength (phase difference of 2nPi) producing a completely constructive interference, the beam that gets back to the source will have and additional half-wavelength path difference (due to that Pi additional phase difference caused by internal reflection) which will produce completely destructive interference.
Sort of correct. Except (1) It's not internal reflection; the beam-splitter has a dielectric or metal coating on one surface, where the reflection takes place. (2) The phase change occurs when light coming through air is reflected by the coating at the front surface. When the light comes through glass and is reflected by the coating (at the back surface) there is no phase change.
@@robinswamidasan cool
What I find more interesting after a second look at this is the number of rings that can be found by moving the mirror back one half the length of the laser chamber. My question is how far back would you have to move the laser back to double the number of waves.
I think you're misunderstanding what the rings are (or, I am). I believe the rings are visual representations of the frequency itself, meaning that the number of rings is neither increasing nor decreasing, but you're just seeing them in different positions. Think of those squishy toys that funnel in on themselves, or think of it like a single string vibrating. We're seeing the same vibration at different intervals of "time", which in this case is represented by distance.
@@holdmeclosertonydanza22 Red, should be a 650nm laser. So, when we are using rings or lines, we can count one ring going from light to dark to light again as a movement of 650nm. However, the laser chamber isn't exactly parallel, it is a rectangle. That gives the edges of the laser a different distance from corner to corner or in this case from center outward. I am of the opinion that there is a formula for laser diameter, chamber length, and ratio of the length of the two outside mirrors.
Interestingly, conservation of energy means that any " disturbance, change of state " in the universe must go somewhere, it cannot be destroyed. It appears to diminish something else must be absorbing that disturbance. It is a relay race that never ends. Therefore, if this is the case the disturbance itself must have received its energy from a previous disturbance. The question is where did the original disturbance come from where the Law does not apply?
Just a sligh press on a table and we can observe length difference between arms... and that's how we directly measured gravitational waves.
i hate it when i google something to answer a question. AND NOW I HAVE MORE QUESTIONS
welcome to reality
What was your initial question
This is beautiful demonstration.
MIT please shoot these old important videos again in higher quality
Beastly performance by professor ezekiel; great job professor!
The topic and the way of explaining is really different from all and really fabolus
Phase of reflected beam changes by pi when it is reflected by denser medium and hence an extra path difference of half wavelength.
Congratulations on getting almost 1,700,000 subscribers and 142,200,000 worldwide views!!
When charge oscillates EM waves emerge from space. During total destructive interference EM waves oscillating in opposite direction cancel each other & dissipate back into space. EM waves are made of Space itself.
Where does the light go? Into the constructively interfered segment of the wave....that's why the constructive fringes are brighter than the un-interfered beam, right? It looks dark where we look into a dark fringe and it looks extra bright when we look into a constructive fringe......what am I missing here, why the mystery?
What if we use cubic beam splitter (that does not add the extra 180 degree phase shift) and have a phase difference of 180 degree between both arm lengths (to and fro)? Shouldn't that have a destructive interference everywhere (assuming perfect alignment)?
This is really really nice demonstration...
I came here for answers, not puzzles. :(
Yes, the "conclusion" is frustrating.
i know right
Welcome to science
Me too - I'm getting sick up to the back teeth of experts DUCKING OUT to leave US with yet another puzzle when they haven't really answered the first question properly - This guy could sent a glass eye to sleep
@ChuckOfNorris:
You quote my thoughts. But I bet the answer is as always in physics: "because chuck norris allows it!"
I could be dead wrong, but if the reflected light (going back into the source) is 180 degrees out of for the direct beam, but not for the beam that gets reflected at the half-silvered mirror as that has to reflect twice on the less dense mirror, and once off of the full mirror. When one of the 2 waves is shifted 180 degrees it results in the constructive interference. In contrast, the original path has an equal number of reflective phase shifts, but the distance traveled is 1.5 times longer in one direction vs the other, such that the wavelength is offset but 180 degrees. Not a physics student so I might be missing some obvious thing here.
You are dead wrong
If you think you can graduate from this college without kissing my kok 🌚
I pulled out some lens polarizers and did some experimenting. I think the answer to the puzzle in the setup is that where there are an odd number of mirror reflections between light of the same initial polarity, there will be destructive interference. Each successive mirror changes the polarity of light. If it reflects off one mirror it is now in the opposite phase, when it reflects of a second mirror it is now back in phase. Also convex lenses do not change phase. And the Professor also added a polarizer after the first mirror after the addition of the beam splitter for the returning light.
Actually, you'll have to read my post and click the wiki link, or look it up on beam splitters... normal mirrors are not phase shifting... But, a splitter 'can' be, but for only one surface, or multiple surfaces depending upon what kind is made.
Because it is not destructive interference. Neither matter nor energy can be destroyed. The first half mirror is working like a switch, with the wave pattern of one beam sending the laser to the detector or back to the laser depending on full or half frequency.
so what happens when they really do FULLY destructively interfere?
There is no such thing as fully destructive interference. The lesson to take from this video is that destructive interference in one location means there is constructive interference somewhere else. In the same way, constructive interference in one location means that there must be destructive interference somewhere else. The total amount of energy in any wave (light, water, sound, etc.) is always the same. Interference means moving the energy from one place to another.
Imagine two people and a rope. What happens is the waves with opposite phase meet at the center point which is not moved at all (destructive interference happens here), BUT the waves will continue travelling and then hit each person with same power as when sent, only the returning wave will have opposite phase then when sent. No energy lost.
@@LiborTinka Interestingly, conservation of energy means that any " disturbance, change of state " in the universe must go somewhere, it cannot be destroyed. It appears to diminish something else must be absorbing that disturbance. It is a relay race that never ends. Therefore, if this is the case the disturbance itself must have received its energy from a previous disturbance. The question is where did the original disturbance come from where the Law does not apply?
@@JohnnyAdroit The confusing aspect of this, is if you have two sinusoidal waves of equal frequency, but phase shifted by pi... Where then would the energy of the waves "go"? Does this effect hold up in 2D?
@@bermchasin If you create/draw a setup (using mirrors and beam splitters) where two beams of light are made to overlap with a phase difference of pi, you will find that the must be at least one other path out of the setup where the interference is not destructive. Try drawing a bunch of systems to get laser beams to overlap. Make sure to keep track of the distances traveled and the phase changes induced by the optical devices. Reflecting off a mirror or beam splitter causes a phase change of pi, passing through a beam splitter does nothing.
about the puzzle, I think it is because of the half-wave loss for backward light on the mirror.
it's like the interference patterns are complementary in each side of an F-B interferometer.
it doesn't disappear it is just cancelled out by the interfering wave, it re appears after the the time period of the wave
Lasing is a quantum mechanical phenomenon , depending on reflections to sustain the lasing action within the laser. The the whole system, optical bench-laser-cavity "lases". The reflected photons are a part of the coherent lasing action and the energy is part of the energy that exists within the lazing volume, just extended in space by mirrors and reflections. This is seen in the last demonstrations with the two beams . There always exists a return beam, except in total constructive . The solution to the last question of the overlap of the return with the forward wave ,when electromagnetic waves are considered to emerge from an ensemble of photons: There exists a very small probability of photon photon interactions , of order 10^-16 if the coupling constants in the loops are counted. It is the same reason that to see the interference pattern one needs material; the photons have a large probability to interact with the electrons in the material.
There is no such thing as photons. All the experiments show lights is waves, never particles. If light is particles, explain where are the particles which have been discarded by destructive interference. The alleged light particles have no charge so they can't mutually annihilate, so they must be laying around waiting for someone to sweep them up and put them in the trash.
@@dreamdiction see this simple experiment where single photons build up the classical double slit interference pattern www.sps.ch/artikel/progresses/wave-particle-duality-of-light-for-the-classroom-13/
the above yutube records an experiment where it shows where the light goes.
@@annavayaki1735 You have obviously never done the experiment yourself so you believe whatever you are told to believe.
What you mistakenly call "single photons" is a high frequency interrupter relay transmitter switch used to produce single separate individual wavelengths, like this ~ ~ ~ ~ ~ not "photon particles".
Continuous waves produce interference patters, intermittent separate single waves also produce interference but at a slower rate/intensity because of the gaps between waves. The interference is the proof that light is waves at all frequencies, never particles. "Probability waves" only exist in researchers imagination, that's why nobody (including Broglie) could design an experiment which shows light is particles.
The photoelectric effect is easily explained by blue light having the right frequency of positive/negative magnetic induction (alternating push/pull) to magnetically agitate a negatively charged election out of it's shell orbit, that's why the photoelectric effect does not work at higher or lower frequencies - nothing to do with "particles". Did you believe red light was waves but blue light magically manifested 'particles' which disappeared again at higher frequencies.
Electromagnetic Radiation (EMR) is waves at all frequencies, all the experiments show light is waves, there is no experiment which shows light is 'particles'.
@@dreamdiction I am a retired physicist, having worked for 40 years in high energy physics experiments, from bubble chambers to the latest large detectors at CERN. Dream on your science fiction.
Enter the layman;--If the act of observation collapses the wave function, then does that not illustrate that there is more than one observer, and that the primary observer has the ability to change the rules of physics at will. Or does it illustrate that these rules are only rules because the primary observer creates the rules?
I don't think this is an observer issue, unless one considers that the observer may draw the wrong conclusions.
Where does the energy go? I thought I’d make a detailed explanation, for those unable to follow the simple correct answers given before mine.
First, we have to make an assumption about the splitters, are they arraigned with the silver and glass sides oriented in the same direction, or is there a phase shift from one or both splitters due to the orientation.
The phase depends upon our knowing what kind of splitter he is using. He doesn't say. Read here for detailed explanation: en.wikipedia.org/wiki/Beam_splitter
Initially, we set up the Michelson Interferometer to display a bright spot at the center of a display to create an interference beam which is constructive along the center which alternates from bright to dark every λ/2 (half wave) (length?) change in the angle. Each Δ of λ/4 in the adjustment arm creates a ΔL of 2* λ/4 or a λ/2 (180°) phase shift.
The splitters ‘usually’ used in these experiments have a phase shifting side, and 3 non-phase shifting directions, just so you can play with effects like we see here. It’s a great test of one’s understanding of the phenomena! This is MIT, who knows; but, it does make a difference, and he does seem to have a 'smirk' in his smile. :-/ I suspect… subtlety! ;-) To understand, one must know ‘precisely’ the processes going on here. This kind of experiment sets MIT apart from smaller colleges and universities. One, for the uninformed, it is a real challenge. Two, for the savvy student, it challenges conceived notions and requires one to examine testing procedures at the level required to make quality experimentation. Imagine if this were to be published as a paper!? How foolish would we feel? This is a great example of the kind of critical and divergent thinking needed today.
In most cases, the primary and principle design and purpose of the Michelson interferometer is solely to show an interference pattern, a second splitter does not get used. As a simple interferometer, whether one leg is phase shifted does not matter.
Note: When I refer to return path, I am referring to the actual return path which is the pass through path from the adjustment arm mirror, which when hitting the splitter on the return is both diverted to the left leg, phase shifted 180°, and passed through in a return path to the laser shifted 0°.
However, in this set up, the paths are "not" the same in how we create the two interference patterns. Though he says they are, the return path beam, which he calls “the other arm” from the adjustment mirror, strikes the back side of the splitter when it makes the 90° turn into the mirror and lens and then on to the screen. The back of the screen introduces a phase shift of 180°. Since the adjusting mirror sets up the interference, this phase reversal has no effect, when using the interferometer as in the first half of the experiement. However, with the introduction of a second splitter, this 180° shift comes into play relative to the reference beam on the fixed leg, with the addition of the interference pattern created for the ‘return’ beam.
It’s interesting to note that if the interference pattern of the first half did actually produce an inverted pattern traveling backwards through the beam, it would phase cancel the entire beam according to Quantum Mechanics, so no reflected beam, this is complex in understanding the fundamental concept behind “Where does the light go”.
What kind of splitter is he using is crucial to our understanding. As an outsider student gleaning information and watching courses from MIT, Stanford, and all the others. I personally think it is a heinous crime to leave out such critical information; there are enough people out there who do not understand this process, and will not take this parameter into account. Someone suggested he would get into trouble if he stated where the light really went; in the case of current affairs he does cater to two schools of thought by removing this critical piece of information. When I first saw the video, I thought I was going to have to dump all my research! He could easily have thrown me by stating what kind of splitter this was, and were I to discover the splitter did not have a phase shifting back.
The interference pattern through the return path does not use the reflecting side of the ‘first’ splitter for one of the legs creating the interference. (This is a critical point, and the whole experiment hinges on this information.) In this case, the ‘return’ legs are both at 0° relative to each other to create interference. This means that the two legs do take different paths than the first, to create the interference pattern for the “return” beam’s path. The return path, before it reaches the second splitter already exists as an interference pattern. The second splitter doesn't do anything but redirect the already existing interference pattern into the viewing leg.
The second splitter, no matter what kind of splitter, does not change the relationship between the two beams already existing as the interference for the return leg because if silvered, the both beams are shifted by 180°, and if glass, both beams are not shifted and remain at 0°. Shifting the interference pattern by 180° does not affect the banding created! Shifting one leg or the other does and in this case, the second splitter has no effect on the interference created prior to reaching it. Note however, it does change the intensity, as each splitter divides the intensity by 50%, the amplitude is affected, but not the phase relationships of the pass through beam from the laser.
To summarize, in the top path, one leg is at 0°, and the second leg is at 180°. In the return path, before it reaches the second splitter, one leg is at 0°, and the second leg is at 0°, therefore the interference pattern is inverted. If we set the first path to create a constructive interference at the center, the return path, not shifted by 180° is destructive; or vice versa, the first path creates a destructive center, and the return path, not shifted by 180° creates a constructive center. What is required to flip the orientation is to change “ONE” path by 180°, but not the other. In this case, the fixed leg of the interferometer is the reference point.
He is incorrect when he says both paths are the same, unless he means the paths of the two legs reaching the splitter is the same. However for the top, the Adjustment leg is phase shifted for the top interference pattern on the screen, but the Adjustment leg is NOT phase shifted through the splitter for the bottom interference pattern, the return path, when displayed on the screen.
The second splitter added later only serves to allow the initial reference beam to pass through (0°), and to redirect the return half of the beam into the second path. Again, since the interference pattern already exists before it reaches the second splitter, reflecting off of the second splitter either modifies both legs 180°, or it does not. Phase shifting the interfered beam by 180° does not change the interference pattern because both legs or beams creating the interference maintain their internal basis relative to one another.
Of course, if the splitter does not have a phase shifting back of a silvered half, then he has proven Quantum Physics (or QM) false. This experiment examines the most fundamental principle of wave function, what happens during destructive interference; the concept that got me interested in Quantum Physics in the first place. Where does the energy go? Are all three vectors phase shifted by 180°, spin, electro and magnetic, or only one, or two? What, if anything, remains observable in reality, when destructive interference happens? If the energy cannot be observed, where is it? The answer can be found in 'complex eigenstates'.
No, because it is unobservable. That's the classical answer. If I might ask, exactly what phenomena are you looking for (I'm not sure); and what is your background?
It's fairly well understood that destructive interference appears to create a 90° shift in the normal, and this is apparently a complex vector. However, in reality, matter interacts with matter, and if the matter interacting has things like electrons and nuclei which they do, then we might conjecture that they also consist of interference patterns which can interact constructively and destructively.
For all we know in a double slit experiment, the light is interacting with the matter of the slit itself at the edges, and the electrons in the material of the edges are altering the phase of the emerging wave. Still the destructively interfered wave points appear at the constructive interference sites. This could be a complex vector reflection being reflected back again by electron interference of the reflecting surface material. [180° is destructive, creates 90° rotation, and at π/2 a surface electron reflects it back] and if that whole pattern is reflected and 180° out of phase with originating phase of incoming. Where does it go? A: 90° complex phase shift. Hypothesizing, of course, that matter is nothing more than a sum of constructive and destructive interference points. (Holographic Universe).
I believe I have a mathematical model of an electron which explains 1/2 spin in terms of simple dimensional interference. (I believe in layman terms we can extrapolate this behavior cognitively by use of simple 2D moire patterns to show the relationship between the math and physical states of matter existing as fixed nodes, and radiating out from that as photons due to resonance.). The problem observationally is simply that the angular momentum of the electron is too fast to observe independant states. For all we know, the electron spends half of its time being unobservable and what we're seeing is the "fan" illusion, where something that appears solid, it really just the blades moving so fast you can't poke your finger between the blades. I feel strongly that we never see the full energy of an particle at any given time, no matter how we measure it. And saying half could be an understatement. We always square everything to get real roots, just to make it observable; that bothers me. It bothered Heisenberg, and Planck and classical convention and politics forced them to describe things differently than they wanted. I think Pauli was in on that too; I certainly agree. The subject was Quantizing angular momentum, and from that we still deal with probability.
I've moved on to Bohmian Mechanics (BM), as from my personal research I think there's better evidence to support that theory, especially with recent entanglement experiments. All along I independently developed my own theory which I later discovered was a variant of the pilot wave theory and BM . The behavior I mentioned about the splitters and is well documented in the specifications of the various types of splitters. The rest is common sense and logics, binary logic in this case which keeps it simple. One need only keep track of the front or back of the splitter, and thus the type. So, on that note: original research of the mind I guess one could say.
So, I'm not really sure which phenomenon you are referring. The experiment fascinated me, as I was hoping to learn something from it. Instead I found neither a confirmation or denial because of lack of information concerning the splitter specifications. So, a poor experiment, in my book, at least in terms of figuring out WIGO, vs WOSIGO, or What is going on vs What one sees is going on.
I'm really just looking for information to prove or disprove my theories. All experiments in my research are mind experiments as I have no laboratory. I call it Phase Theory, not to be confused with the Wikipedia Phase Theory that's been around a while; but, I've focused on constructive and destructive interference. Science has spend a lot of time and experimentation and development of constructive interference (Phase conjugate mirrors, Star Wars Defense, Holographic Identification, Photon doubling, Atmospheric interference corrections in Astronomy to name a few), but makes little to no effort to examine the destructive interference effect, and that it appears to be a gateway into N-space dimensional interference, primarily because of the "Where does it go" phenomena, and that based on QM and BM the effect is usually complex, and thus defined as "unobservable" in QM terms as in some aspects of entanglement has shown, unmeasurable.
Entanglement claims to disprove the local hidden variable theory; but, and I'm still absorbing BM, and my theory theorizes a possible local hidden variable which can't be accounted for in current experiments. But, it's an N-space problem, and not easily observable if at all, thus mind experiments.
So, based on my key word usage, these are areas you can read about.
+David C. Huculak Wow! Thank you, a very nice post. I'm more used to internet Trolls that defend as if their life depended upon it, a 3D observable universe, and anything contrary to that concept, freaks out their little monkey brains. lol
I learned about uncertainty, and quantum mechanics much later in life. I abhorred the probability approach until I understood it. It took much doing because everything I had come to understand didn't allow it; but, at that time I couldn't imagine wave function.
I really became serious when I was 30 years old, I'm 61 now. I had read a book written by what many would still today call a goof ball, and paid little attention to him. I felt, if I were to learn to think out of the box, I had to destroy the box first. So, I never limited myself to solely classical studies; and I'm self taught all the way pretty much, that is except for college and university level math, physics and calculus. I am self taught in linear algebra, and with that the translational geometrical identities, rotation, translation, etc. Much needed to understand classical Quantum Mechanics. Heisenberg's uncertainty requires a mental image of wave function to see why it doesn't specifically conform to linear vectors, however the wave function follows basically a vector form, like a spiral around a vector.
I realized anything I decided had to agree with anything we'd observed in physics to date. However, I also realized that it would only have to conform to observables, a term I later used and interchangeably with the term 'reality' and decided to call anything that was beyond observable geometry as existing, or saying instead of reality, existence even though it didn't specify to what level it exists, like a thought experiment. It's more complex than this; but, it suffices for the time.
In the book I read, the "scientist" made one statement I pondered for several years. He stated that a photon was an electron rotated out of phase by 90°. Already familiar with both electrons, and their parametrics, and photons and their parametrics, I observed that they were very similar indeed, almost too similar, it seemed strange that they were so similar.
In fact, at the time, the only difference I could see between the electron and photon was that one (the electron) had mass, and moved slow; and the other (the photon) was 'massless' and moved at the speed of light. Other than those two things, they were nearly identical. I didn't believe in coincidences, except maybe randomly.
When I tried to discuss this with my professors, or other learned men, I was either way over their head, or they rejected me outright without thought, which confused me, as I was just making inquiry, not a statement of fact.
That was 30+ years ago.
My first hero was Einstein, and my second was Nikola Tesla. Through Einstein, I was interested in time and light, and through Nikola, I was interested in resonance; this led me to constructive and destructive interference which is present in photons. When I was 12, and I saw my first electromagnetic chart, my mind imagined that based on what I was seeing, matter must be at the very low end of the spectrum, and have a very long wavelength. Such is the naivete of a child. But, I never lost my curiosity as to whether everything was just part of the EM spectrum.
I also noticed on a map of the globe, that all the pieces fit together somewhat like a jig saw puzzle. I thought this curious, and that was 1968 long before plate tectonics was known. But, that's another story; I'm interested in a lot of things. And I am one of those strange kind of people that just can suck up everything they read; although, my years are starting to show... to me.
I am either unemployed right now; or, I am retired; not sure which being 61. But, because of an auto accident 10+ years ago; I'd definitely say I'm disabled as I received as a passenger really bad back injury which limits my present physical abilities, though one can hardly tell to look at me. But, it forced me to completely give up most physical activity, and I therefore only had my mind to work with. Thank goodness, I was interested in just about everything; but, loved physics, and philosophy, computers, etc.
So, I consider my hobbies, my work, and right now "my" Phase Theory" and supporting activities take up most of my time, with some 'shiny object' distractions. I'm getting older; but, I'm currently studying python (a programming language) with the eye towards modifying Blender, a extremely sophisticated 3D drawing tool so that I could make n-space objects and the mathematics surrounding their behavior. The spreadsheet was much too limiting.
I would give just about anything to have some people helping me; as I see it, unless we're all "changed in the twinkling of an eye" I'll run out of time before I develop FTL(sic) and matter teleportation; I think QM energy sources are on their way into the public as we speak, several if what I see emerging is what I think it is. I can even explain how they work, though the developers are a little hazy on theory; they're more like Tesla, a real hands on guy. My best skills are multi-dimensional spatialization, and an intuitive grasp of the math. I would love to find a like minded peer or two or more!
So, no job; but, I do physics full time! :-)
I believe the gateway to the greatness of the cosmos is in understanding the role of resonant coherent destructive phase cancellation. Controlled, of course XD.
I hope this isn't too long. I could lecture, discuss or have discourse on these topics ad nauseam... not to me, of course ;-) I would love to specifically find someone who could show me where my thinking has gone awry! Or, in other words, where I'm wrong.
I became interested in phase conjugation in 1980-81. My first 'aha' moment in Calculus *theory* occurred in 1981. Applied calculus was too mundane. Any suggestions, help, information, discussion, you name it, you could provide would be greatly appreciated.
Thank you for asking! PS: I haven't played in a while; but, while I did, I loved playing Go! Unfortunately a lack of playing partners that could compete forced me to move on. It's been 20+ years since I played, fascinating game, so many permutations.
+Chip Cooper Can you at least provide figures for your explanation? some of your terms in your explanation are rather ambiguous, for like, "left leg", "back side of the splitter", "The back of the screen introduces a phase shift of 180 degree", "first splitter", "viewing leg". Can you at least unify the terms? Also, I'm not sure I understood "return path" from your definition, though I get grasp of it
Jeong Hoon hard to believe that I wrote that less than two months ago. Seems like ages. I don't exactly recall; but, I tried to use the terms he uses in the video when I could for consistency. From what I do recall, we have the interferometer, and the extras he added to make the return trip.
I know when I refer to the back side of the splitter; I'm referring to the different types of splitters, and we don't know what type he's using here. But, splitters *can* have a mirrored side and a glass side. Without reviewing what I read, the back side of the splitter would have been referred in this case to either the one that does a phase change vs the side that doesn't cause a phase shift. I believe I set up which is which when I discuss different splitters. (This is just a quick response; I can't get into the test right now. I'm working one a spinor based n-space mathematical model of a 1/2 spin particle at the moment, purely theoretical, of course.
So, let me copy your response and take some responses there from memory.
+Chip Cooper Can you at least provide figures for your explanation? *I believe I used his set up as viewed from the front of the table, closest, the narrow side) some of your terms in your explanation are rather ambiguous, for like, "left leg" (probably the return leg he added later), "back side of the splitter" (explained earlier), "The back of the screen introduces a phase shift of 180 degree" (refers to the atomic and subatomic structure of the screen acting upon the interference pattern making the light visible), "first splitter" (the splitter first in path after emission from the laser), "viewing leg" (not sure, the leg to the screen).. Can you at least unify the terms? Also, I'm not sure I understood "return path" from your definition, though I get grasp of it
If this isn't enough, write back using Google+ notifications, and you can tag me in there. UA-cam stopped allowing tags on the UA-cam video web page, and it's only active in Google Notifications window, like I did for you. I'll look again and re-read what I said, so I can clarify. As I recall, it took me some thinking to follow all the paths. I drew myself a diagram; but, don't know where the notes are, if it wasn't just an envelope. I've spent 30 years thinking about deconstructive interference. I think the term destructive is a misnomer, and that phase cancelling vectors are a well kept secret, or completely ignored subject area in physics little understood. Thus the question, where does it go. This has answers to the double slit experiment, if examined properly. However, keep in mind, we don't know what type splitter he used. Some don't have the 180° phase shift on one side, some do, it's a critical part of the critical thinking, as I'm sure you have or will realize. I don't know if as instructional, it was intentional or not, leaving the piece of data out of the video. It certainly hampers drawing a definitive conclusion.
I apologize, but it would take me almost as long to redo this experiment, done mostly in my head, as I did before. I only need to write down where the beam was phase inverted, in a binary form. 0 for no shift, and 1 for inverted, the rest is logic and following all paths.
I have been picking up a 3D drawing program Blender so that I could eventually draw these and create a video.for more complicated explanations. This might make a good first project for me as I've gained some skill since I wrote this post. Blender is written in Python, and I hope to familiarize myself with it, as I'd like to modify the drawing program to handle n-space vectors and spinors adding some controls to limit viewing areas to 3 orthogonal dimensional constraints. It's hard enough to imagine 3D on a 2D screen, fortunately as humans we're pretty good at that. However 6 or 9 dimensions, not so much.
I have my weak areas, and I'm picking up missing information as quickly as possible; although I have been working on this abstractly for over 30 years.
+Chip Cooper Wow, your response is immediate! I wonder if I can send you privately? I want to send some diagrams I've drawn, and see if it makes sense, because in my diagram, both the interference at the screen and interference of beams to the source make constructive/destructive simultaneously!
It’s called the ether. Light isn’t a thing no more than a wrinkle is on a shirt. Light and matter are magnitudes which you should conceive of as
what about setups that dont have returning rays ?
more important in where does the energy go?
One question... the effect that you get constructive interference at one output while you get destructive interference in the other output is due to the induced phase shift for one of the interferometer arms. So if you could take a beam splitter which does not induce any phase shift or symmetric phase shift for both arms, it should be able to eliminate the complete light... Right?
in wave theory yes. the light has to cancel out if theres complete destructive interference
The answer to the last question is simple. When the two lights were interfering destructively, they already have an effective path difference of lamda/2. Now, in case of the light totally sent back to the source, an additional path difference of lamda/2 is introduced in one beam of light making the total path difference an even multiple of lamda which is the condition for constructive interference.
still didn't explain what the photons are doing when the screen is blank. Do the photons still heat up the surface even though they are not visible?
There is no photon when the screen is blank.
Photons do not exist, that is the forbidden secret that he afraid to admit.
thanks for this video but what about the emf and it is interaction on laser beam
Which side of the center lens does light reflect off of. Does it always reflect off the front side or always the backside? (Front being the incident side)
seems pretty important to answer the question
How is a beamsplitter actually made? Usually it is
a piece of glass with a dielectric or metal coating on the front surface. Light striking it from the front has a 50% (or any other value, depending on the coating) chance of being reflected, and a
50% chance of being transmitted. In the case of a dielectric (non-conducting and non-magnetic) a reflection does indeed induce a phase shift of π, whereas a transmitted photon picks up no phase shift.
Details: www.cs.princeton.edu/courses/archive/fall06/cos576/papers/zetie_et_al_mach_zehnder00.pdf
More: What happens to a photon approaching the beamsplitter from behind? There it first enters the glass (ignoring the small chance of reflection off the air-glass interface) and has a 50% chance of reflecting off the dielectric coating whilst within the glass - this reflection does not induce a phase change.
Ok so noise canceling headphones use disruptive interference with sound. so why hasn't anyone used this same concept to build a real Light saber yet?
Say you have 2 laser on exactly opposite frequencies pointed at the same point in space shouldn't they cancel each other out? Thus stopping both lasers at that point essentially creating a real light saber. Just wondering why no one has done this yet.
No one has done that, yet, because it's impossible. Interference is not an actual interaction. It can't and does not stop energy flow. We did show this to you in school with wave experiments, by the way. You were simply not picking up what we were trying to explain because it's not completely obvious. It escapes most students, including myself. I didn't understand this correctly until I took a math class in university years later.
Cant you do the same thing with sound and thats what noise cancellation uses
Can anyone explain to me how the beam "knows" it's going to destructively interfere after traversing the beam splitter (i.e. meeting the other reflected light beam), so that it decides to reflect instead? To me this appears as if the light can "look" into the future, something like "Hey, it seems as if I am about to destructively interfere with another light source an inch ahead, therefor I must reflect off this surface instead of transverse it.".
If I understand your question, the thing is you are thinking light is interfering at the screen, while the destructive interference state is present right at the point they mix. No light departs from that point to the "destructive interf. arm".
Very interesting!
Why didn't he describe the experiment by using diagrams? It would be much easier to follow. Otherwise it is a great video.
What if light creates matter? Or matter can not exist without light?
real electron positron , duel production from light
Light can not create stable matter. It can, at most, create an electron-positron pair. Unless you have a way to safely discard that positron, your electron won't be around for too long, either.
great job ! I solved my own puzzle
Is this how the FBI and other spy agencies listen to terrorist planning terror acts as they point a laser beam (which doesn't have to be visible beam and can be infra red laser, such that window panes reflecting the beam gets modulated by sound waves and the spy agencies can listen to enemy, I could see as you were speaking the beam was modulating as well as when you pressed on the table.
You've made a light switch!
I don't know that it's not possible. If waves cancel eachother out then the energy is destroyed. Is light just a packet of energy? If so then light can be destroyed through destructive interference.
how the single light returning to the source is interfering with itself?
Yes it does, but If you knew why you'd have solved one of the most enduring mysteries of physics-the interpretation of quantum mechanics :)
I have a feeling cats are involved
Where does the energy from both sources of light go?? Because it seems it is being destroyed when we know that's not possible.
what i am watching is that the beams in screen are even sensitive to his voice!
Ti -CO2 They are I noticed the same thing
If I press here....??? What is going on?
that explains chemtrails blocking out the sun
It seems like it's tough to find that sweet spot where the light disappears. He has to press on the bench to fine-adjust the distance?
That's because red light is ~ 800nm in wavelength and we need to shift a beam by 400nm , it's hard to make an object not move by that ammount, even sound vibrations would ruin the interference
sooo...whats the answer professor....????
So.... What is the answer? I am looking for this for 5 hours....
I recently posted what I hope is a definitive explanation. You may want to read it.
hey anyone got the answer ? i still can't find it
Your electrons are pos and neg and cancel each other out by interrupting them. they influence the freq.grounding can change things.
Guess MIT needs to invest in a better table
I had a blue lightIf bulb at 150 watts what would the green watts be in balancing watt to wavelength?
Why so many mirrors and a lens?
keep pushing the table and you might break the matrix
7:30 Demon Headmaster.
THIS!!! Is how the UAPs are cloaking!!
Sleepyeyeguy;--The "law" of the conservation of energy says that nothing is ever destroyed. It is merely converted into matter, light, heat, or motion. So when the interference pattern shows that two waves of light interfere with each other, then that light must disappear somewhere,(or somewhen). Or, maybe we are now observing the first concrete evidence on Earth of "dark matter". It appears dark to us, but in a parallel universe, it becomes light.
+Tony Boyle Dark matter doesn't interact with light, hence the name.
The light vanishes from view but it does not reappear in another universe and it does not have anything to do with dark matter. Does the ocean vanish and reappear in another universe when its waves cancel out? You're just adding opposites. 1 plus -1 equals 0. Everything is conserved.
Ah but a photon only "appears" when it interacts with something.
Hence when the waves cancel, the photons simply don't produce an interaction. What happens? They keep going where they're going!
I can explain this result of experiment considering the light as a photon(particle) not wave
I'm sure you can, Mr. Crank Physicist.
@@dr.s-2 i am not a physicist
@@gadhiyafalgun273 That's correct, you're a crank physicist.
@@dr.s-2 i am not physicist ,okay if you still not get it then it seem you are some what stubborn
If light is particles, explain where are the particles which have been discarded by destructive interference. The alleged light particles have no charge so they can't mutually annihilate, so they must be laying around waiting for someone to sweep them up and put them in the trash.
كلشي مفتهمت
I apriciate n wunder this same as in twinflame path of relationship
❤
am confused!?
That's because he left out information. This is a part of an MIT course, and a problem... note the '?' question mark. Think of it as a voluntary quiz. Read other replies for the answer... some are right, some are wrong.
The questions in this experiment are legion, but the major one is this;--How much intelligence must an observer have to collapse the wave function? Can an insect, (or insects), collapse the wave function? How about a cat, or dog? If any observer, (no matter the species), observes the experiment at a later time, can they then collapse the wave function? These primary questions should not be obfuscated with math or creative scientific language by those who do not wish to reveal that they do not understand what is happening here, any more than we do.
No intelligence is required. A camera can collapse the wave function. You may sometimes hear of an "observer" collapsing a wave function, but really it is a measurement that collapses it.
To try to explain it in un-obfuscated language; how much intelligence does it take to measure the width of a blade of grass? Its width is "unknown" until it's somehow measured. But an insect can "measure" the grass (by stepping on it and having a sense of its size), as can a human, as can a totall intelligence-less camera (by taking a picture and knowing how far away the grass is).
Zachary Jenkins "A camera can collapse a wave function"? How can you know this without observing the picture from the camera?
terry wilder Now you're starting to get it ;) It's not collapsed from your point of reference until you observe the camera.
Zachary Jenkins So what you stated is false.
No, it's true! It's about frames of reference. "Collapsing the wave function" is not a universal concept, it occurs only within a given frame of reference. A frame of reference does not require "intelligence" or "consciousness." The camera's frame of reference is different from yours. When the camera observes the grass (or whatever), the measurement is done from its frame of reference. When you observe the camera's results, the measurement is then done from YOUR frame of reference. Get it?
Now all the light returns to the source... oh wait... (laser explodes)
Isolator xD
The light does not go anywhere . Light does not imit anything . It's like everything you've ever known including the earth and the sun and the moon is flowing through a river a continuous river . And when you drop something say a rock in the river it forms an attraction current like an eddy . Light is the same . Everything is The light .
Complete and utter bollocks! Does not answer the question in the title at all!
He knows the answer to this puzzle but realizes he will loose his job if he talks about it.
I think it's simpler than that, I made a post give what I hope is a definitive explanation.
Instead of solving a problem, leave us with a riddle. Thanks. Video must be very old since a light pen would have worked. Looked like he had part of cern on the table. LOL
Give up .
So there is nothing called destructive interference of "E.M" waves.
obedient lunetics
clear as mud
should have used diagrams and not hand waving
I like so much when they scientifically BS me :D