The Double Slit Experiment
The Double Slit Experiment
It is probably the most important experiment for the credibility of the wave theory of light. But how seriously should it be taken?
If you look at the different links below and compare them to the images of so-called constructive and destructive interference (you may use this video as a quick introduction), you will see that it is far from being the undeniable proof it is always presented to be.
In fact, it looks simply like the original image on which a sheet with multiple splits have been laid.
https://thephilosophyforum.com/discussion/comment/109433
https://thephilosophyforum.com/discussion/comment/109454
https://thephilosophyforum.com/discussion/comment/109028
https://thephilosophyforum.com/discussion/comment/109162
It is probably the most important experiment for the credibility of the wave theory of light. But how seriously should it be taken?
If you look at the different links below and compare them to the images of so-called constructive and destructive interference (you may use this video as a quick introduction), you will see that it is far from being the undeniable proof it is always presented to be.
In fact, it looks simply like the original image on which a sheet with multiple splits have been laid.
https://thephilosophyforum.com/discussion/comment/109433
https://thephilosophyforum.com/discussion/comment/109454
https://thephilosophyforum.com/discussion/comment/109028
https://thephilosophyforum.com/discussion/comment/109162
Comments (52)
If you google this expression, or search it on Youtube, you will find and see many examples of such an original device. I would say that a multiple split grating is something like that. It creates multiple images of the original scene, and that is what we see when we shine a laser beam to such a grating. Through every split a small image of the laser.
http://www.thescienceforum.com/personal-theories-alternative-ideas/
Your posts here are off-topic.
No, I don't see any reason to doubt the standard approach. You will need to present either evidence or an argument.
1) One of the main arguments in favor of constructive and destructive interference is presented in a very understandable language by the Khan Academy.
The idea is as simple as it is powerful. Light rays, or rather waves, move towards a point, and for that they travel a different distance according to their start position.
The difference between two distances determine whether the waves reinforce or negate each other. If the difference is one wave length then we have constructive interference, and by one half-wave length, destructive interference, with all gradations in between.
2) There is something peculiar about light waves. Unlike water waves whose wavelength play no role in the crossing of a split, as long as the split is high enough, for light waves the height of the split is apparently essential.
The wave length is defined as the distance between two peaks two troughs.
Imagine now that the wave has to go through a split as high as the amplitude of the wave, that is the height of the wave. The only obstacle to the wave will be formed by the width of the split since its height is more than sufficient.
But the width of the wave has, as far as I can see, no relationship with its wavelength.
For two waves to go at the same time through a split they would have to have a width each at most half that of the split.
I have not found any indication that the width of the wave played any role in constructive or destructive interference.
3) Something else. Water waves go up and down, but that has nothing to do with any kind of interference per se. It is a simple matter of gravity. Whatever goes up must come down.
About two waves colliding with each other. I can certainly imagine that the water will go higher than any of the waves through the collision, just like flying debris when two cars collide, but that's it.
The whole, mathematical concept of wave is based on the dichotomy peak and trough whereby the first is a positive factor while the second one is negative.
But a trough, at least as far as water waves are concerned, is, once again, the result of the water coming back down. There is not somehow a movement opposite to the the one creating the peaks. In fact, all the energy goes into creating those peaks, the troughs being more of a secondary phenomenon.
The mathematical picture of waves may have its uses as far as calculations are concerned, but it certainly does not give a realistic image of reality.
4) According to the theory, different points, or different waves, go to the same location. Transposed to image formation it would seem that from every point on an object rays are propagated to all points of the image.
Each point of the image is therefore the final and random result of the combination of an infinite number of rays. Statistically speaking, each image should contain as many cases of constructive as destructive interference, especially if it is a monochromatic image. A red object could therefore never look entirely red.
What is a split?Did you mean slit?
Quoting Hachem
So what? That is, what conclusion do you reach from this?
Quoting Hachem
If the mathematics allows us to predict results with great accuracy, then hasn't it ipso facto provided a realistic image of reality?
Quoting Hachem
Not random; and why the switch from waves to rays?
Try looking at it using Bohm's version of the Quantum Potential which doesn't move through the slits but rather affects the "particle" by form. It much better, and yes mathematics is all symbolic. It has no relevance to what actually exists because it can't. It only provides some limited predictive measurements.
Bit of a self-contradictory wish. If the universe is indeterministic, then the cause-effect chain is ineffective. Control does need cause-effect chain to be working. But it's not. So control is impossible, in a non-deterministic universe.
I am afraid I do not share the metaphysics of the Copenhagen school. I do not believe the particle is in anyway affected by mere observation, and I certainly do not believe that it can go through two slits at the same time. This is only considered as possible because of the theory of the dual nature of light.
That is what I am trying, painstakingly, bit by bit, not to prove, that is I think impossible, but to at least show as plausible.
This is at the same time an answer to szardosszemagad.
Choices are constrained and affected by the past memories but are non-deterministic in nature. Because of habits, the universe is probabilistic.
I remain firmly deterministic. Call it a metaphysical prejudice.
Well, that's your choice.
Isn't determinism and probabilistic outcomes two sides of the same coin? It's just where you want to place yourself in time.
Let us say that, if there is something like a photon, I am convinced it goes either through one slit or the other.
https://philpapers.org/post/23274
There is a huge difference between trying to place oneself in time (duration) and being placed (the block universe).
I would be inclined to agree with you with the following distinction: there is nothing probabilistic about material processes, only about our knowledge of them and how we react to them.
Observe what is really happening and not somemodel that some philosophers, or scientists, or science fiction writers have created. Most of what you read are just nice stories. If you are interested in learning about nature then observe it. If you are interested in writing stories and reading imaginative stories, that is fine, but it gets you no closer to understanding nature other than observing the human mind can be quite creative.
There is no evidence in quantum mechanics or otherwise to support this idea. All evidence is to the contrary. However, one can believe what one wishes to believe.
Please remember that this thread is about a light phenomenon, and not about consciousness. That would also be my plea to Rich, not to drown this thread in more general issues, however exciting they may be.
Just let me respond to Rich and I'll drop the subject.
Quoting Rich
So you are arguing that there is no universality to something... I'm rushing a bit. What is it that has no universality? Time?
If you want to respond in one of my threads (preferably the one nobody has read that would be fine :) )
There is duration which is exactly what you are experiencing: memories, possibilities of future actions, choices.
They are ultimately intertwined. One cannot understand one without the other. Treating light as a wave or particle gets one no where. The ancients were on the right track. Light is about the spirit.
Quoting Rich
If you're up for a chat about it come across to The First Few Cognitive Steps Required to Believe in Primordial Soup Theory - I've responded to you there.
Your answer "Choices are constrained... etc." is not a direct response to my observation, furthermore, your answer is full of wishful claims, without any validity to them.
Your analysis, Quoting Rich is not at all logical. It is a claim, but it has no merit, due to lack of evidencing or other support. You just make up things as you go, is my opinion.
If determininsm was false, then the world would be non-causal. If the world were non-causal, then the rules and laws of QM could not be drawn up.
The rules and laws of QM have been drawn up. You accept they have been.
Therefore the world is causal.
Therefore the world is deterministic.
Your argument I proved wrong.
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I challenge you to name one, just one rule of QM which is well-known in the public's awareness, and shows that its process is not causal. Thanks.
Wrong. There are causes but constraints, choices and novelty make the world probabilistic.
As for turning the QM probabilistic into a deterministic equation, well that is even more strange than determinism itself. Faith dies hard. But, as you wish.
Human knowledge of the future states of the world is probabilistic. But the world itself, its future states, is determined by its past, via a chain of causality.
What the heck? There is nothing in QM that is causal. Bohm's interpretation is causal but non-deterministic.
That may be your own personal interpretation, but your opinion is false.
It is simple to adopt a deterministic view of the universe. All one has to do is ignore that s/he is adopting it.
I have no interpretation. There is zero determinism in QM. Never was and, as far as all evidence to date, never will be. Probabilistic behavior is baked into the universe as is the probabilistic wave. However, anyone is free to have faith that this may someday change as others have faith in the Second Coming. It is human nature to have faith.
Allow me to start with an image already displayed, an open camera body, no lens, and a laser pen directed at the center, more or less, of the mirror.
The first picture has been taken at 1/400s. All images were set at ISO 100.
You will notice the bright and dark circles that appear in all experiments where interference phenomena are said to be studied.
This picture has been taken, allow me to emphasize this fundamental fact, with nothing between the camera and the laser beam. Since the mirror is drawn up at the moment of exposure, these rings have to come either from the pen itself, the sensor diodes, or both.
The following pictures have been taken with an Anti Newton glass, one part of a slide frame, taped to a body cap on which a hole with a diameter of approximately one centimeter had been drilled. Notice that the so-called Newton rings are still present, but only visible at short exposures
At 1s, no rings are visible.
At 1/1000s, the rings are clearly visible.
The following picture has been taken again with an anti Newton glass taped to a body cap, but this time I had made the opening much larger to avoid any misunderstandings concerning diffraction phenomena.
The lower dark half is an artifact due to misalignment of the slide. The exposure time was 1/4000s.
I thought these pictures might be interesting for people familiar with the phenomena of constructive and destructive interference, as well as with the so-called Newton rings. I wonder what they make out of it.
Since Newton rings are always presented as being the result of at least two surfaces pressed against each other, creating minuscule differences in the distances between one surface and the other, and therefore creating the rings of constructive and destructive interference, I wondered what would happen if I used both glasses of the slide, and not only one. Would the rings disappear entirely?
Apparently not.
The first picture has been taken at 1/4000s, and the second at 1/320s. The rings are definitely less pronounced as before, but still there. Would better quality glass eliminate the rings completely?
But why are they present in the first place when only one glass is used?
Again, a puzzle for whomever believes in interference phenomena.
I find the following picture quite intriguing, especially when you consider how the camera reacted. Instead of a laser pen I used a flash light and directed the beam, as before, through the opening of the camera body. When I looked at the Lcd screen I saw white and black bands scrolling down, in a regular fashion.
Imagine black bands like this one being alternated with white ones. It was taken with 1/1000s.
I found the scrolling very peculiar and have no explanation for it.
In fact I was trying to show the pattern my electric torch left on the wall, or a screen. A rectangular pattern of bright and dark bands. Maybe this image is just a part of it.
Anyway, I think that, just like when taking a picture of the sun, we have to adjust our exposure speed to get the sun in the picture, instead of an all encompassing white blob.
What we are seeing each time are not the light rays, but the structure behind them.
This is how the same picture looks like when a red (dark orange) filter is placed in front of the torch.
Except for the color, nothing is changed as far as I can see.
This reinforces me in my conviction that what we consider as properties of light are most often simply the properties of the light source.
I am sorry it took so long, but I just got the slide in the mail this afternoon. It concerns a slide (50mm/50mm) with two slits of 0,013 mm each, separated by a distance, from center to center, of 0,1 mm.
As usual, I taped the slide to the body cap of a digital camera. The cap was almost completely open, having kept only the outer periphery to attach it to the camera body.
I will let you draw your own conclusions but it seems to me that what we are dealing with is simply a slice of the image we got when nothing was impeding the laser beam on its way to the camera.
In other words, the concepts of constructive and destructive interference are completely superfluous!
1/4000s
1/2000s
1/1000s
1/200s
1/60s
1/15s
1 second.
3 seconds
The partial text on the upper right corner are some markings on the slide and irrelevant to the double slit experiment.
I have used a simple application any Windows user have at his/her disposition, Paint. What I have done is take one of the pictures of the rings formed by a laser beam om the camera sensor, and deleted everything but a very thin slice.
I hope to show that the so called double split patterns of constructive and destructive interference are nothing but the original image seen through very narrow slits.
The principle of interference, and wave length, depends on the actual distance a wave or a ray is supposed to travel between two points.
A simple way of altering the distance between two points is to rotate the screen slightly around its vertical axis. This way, some distances would become (slightly) shorter, while others would become longer.
By subtly changing the position of the screen, one should therefore be able to transform a dark ring in a bright one, and vice versa.
Shaoul Ezekiel seems to be doing just that. Except that his setup is much more complex and involves mirrors, lenses and beam splitters.
The setup with a light source and a screen is much simpler and easier to interpret: does distance play a role in the formation of dark and bright rings?
I invite you to see it for yourself. I cannot show it to you because it would need more a video feed than still images, but I personally could not detect any effect.
Please do not take me at my word!
Double slit experiments are usually presented in a very abstract manner. The light source must be monochromatic, and it is at the same time the sole object present in the experiment.
I present here pictures taken with a zoom lens, the first one free, and then with the same double slit slide I used before, taped to the lens, directly on a UV filter to avoid damaging the pricey glass.
The first pictures show in fact a double image which may be confusing. I could have just covered the letters on the slide (I think they represent the width of the slits, 0.013, but I am not quite sure), like I did for the last slides.
Notice that instead of interference patterns that always seem to be present when slits (single, double or multiple) are used, what we see is a picture, rather unsharp, representing a very recognizable part of the scene first taken with the uncovered zoom lens.
There doe not seem to be any mysterious or magical processes behind the obtained results. They are what we would see it we could look through the slits with our own eyes.
Unhindered view of one of my bookshelves. f/5.6, 1/20s, @ 92mm and ISO 100
The circle represents the text on the slide. Notice that the space between the slits does not appear on the image at all. Such a phenomenon was one of the main reasons Newton's corpuscular theory was abandoned. Exposure time 15seconds.
The circle has been covered by dark tape. 10 seconds.
even under relatively very short exposure times, the whole scene
is still visible. 1/3 of a second.
There is something very interesting in the preceding, but also in the following images. Objects seem to react differently from light beams.
Look at how the laser beam is apparently reproduced over and over again.
The books, on the other hand, are shown only once. The board dividing the two shelves, and which should probably be hidden by the space between the slits, seems to be projected two or three times.
What I think is happening is that the laser beam, just like the books, also is reproduced but once. With maybe unsharp features here or there because of the divide.
I will certainly not claim of being able to explain all the features present in those images.
That is the whole issue right here. Cosmology is metaphysics for scientists.
But then again, another general objection, a show of loyalty and no attempt to look at the issues themselves. I understand if you feel you have nothing to say on these problems, but please do not then decide for others what the nature of these problems is.
,Quoting bill harris
Einstein and Bohr had to change their view of reality, space and time. And not (only) in a technical way.