RIP Professor Ziggy Ezekiel.

This is beautiful demonstration.

Beastly performance by professor ezekiel; great job professor!

Congratulations on getting almost 1,700,000 subscribers and 142,200,000 worldwide views!!

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.

This is really really nice demonstration...

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

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?

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)?

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.

i hate it when i google something to answer a question. AND NOW I HAVE MORE QUESTIONS

Just a sligh press on a table and we can observe length difference between arms... and that's how we directly measured gravitational waves.

The topic and the way of explaining is really different from all and really fabolus

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.

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.

Phase of reflected beam changes by pi when it is reflected by denser medium and hence an extra path difference of half wavelength.

thanks for this video but what about the emf and it is interaction on laser beam

what about setups that dont have returning rays ?

great job ! I solved my own puzzle

Very interesting!

I came here for answers, not puzzles. :(

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?

MIT please shoot these old important videos again in higher quality

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?

about the puzzle, I think it is because of the half-wave loss for backward light on the mirror.

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.

it's like the interference patterns are complementary in each side of an F-B interferometer.

Does this imply that the appearance of starlight appearing and disappearing is caused by a single source of starlight having interference?

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.".

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?

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.

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.

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

Cant you do the same thing with sound and thats what noise cancellation uses

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?

it doesn't disappear it is just cancelled out by the interfering wave, it re appears after the the time period of the wave

more important in where does the energy go?

how the single light returning to the source is interfering with itself?

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.

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 had a blue lightIf bulb at 150 watts what would the green watts be in balancing watt to wavelength?

You've made a light switch!

What if light creates matter? Or matter can not exist without light?

what i am watching is that the beams in screen are even sensitive to his voice!

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'.

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.

7:30 Demon Headmaster.

❤

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?

sooo...whats the answer professor....????

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?

Why didn't he describe the experiment by using diagrams? It would be much easier to follow. Otherwise it is a great video.

am confused!?

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 explains chemtrails blocking out the sun

Why so many mirrors and a lens?

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.

So.... What is the answer? I am looking for this for 5 hours....

I apriciate n wunder this same as in twinflame path of relationship

كلشي مفتهمت

Where does the energy from both sources of light go?? Because it seems it is being destroyed when we know that's not possible.

I have a feeling cats are involved

keep pushing the table and you might break the matrix

Your electrons are pos and neg and cancel each other out by interrupting them. they influence the freq.grounding can change things.

THIS!!! Is how the UAPs are cloaking!!

Guess MIT needs to invest in a better table

I can explain this result of experiment considering the light as a photon(particle) not wave

Now all the light returns to the source... oh wait... (laser explodes)

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.

He knows the answer to this puzzle but realizes he will loose his job if he talks about it.

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.

Complete and utter bollocks! Does not answer the question in the title at all!

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

obedient lunetics

I like so much when they scientifically BS me :D

Give up .

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 .

clear as mud should have used diagrams and not hand waving

So there is nothing called destructive interference of "E.M" waves.