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Has the double slit experiment been done and verified in a vacuum? I'm able to produce the superficial results with a simple neon laser, but it always struck me

by ksaj 7y ago

Has the double slit experiment been done and verified in a vacuum? I'm able to produce the superficial results with a simple neon laser, but it always struck me that outside a vacuum, there is a lot available to skew those results.

gus_massa 7y ago
> Has the double slit experiment been done and verified in a vacuum? 99.9999999% sure yes, but I can't find a source with the actual experiment. The versions with electrons are made in vacuum, but I'm not sure they use the double slit pattern. You can reproduce the experiment with light in air. It's expected that you will get the same result in vacuum. An actual experiment is nice, but the setup in more complicated, so it's not done in a normal lab class. It should be easy to setup for someone with access to a vacuum pump, and some free time (1 week top). It would be nice to see how the lines move when the refraction index of the air that is almost 1 changes to the refraction index of vacuum that is exactly 1. It's hard to convince someone of doing the actual experiment, because it looks a lot of work without an insightful result. Perhaps you are lucky and someone already did this. I guess this is the case, but I can't find it. Perhaps you can convince someone like Cody of "Cody's lab" to make the experiment and upload a video.
- ksaj 7y ago
  Exactly. Lots of food for thought there. I expect these results in the open air, since there is so much for the photons to bounce off of. They're probably even bouncing off the sides of the actual slits, unless the block is thin and precise enough, and anti-reflective enough to not allow light bouncing off of it - straight polarized lines only. This is why I ask such a specific question. I don't deny the effect is happening at all - I question the influence of other parts not taken care of in the experiment. We speak of "noise" (interference) when discussing related observations in regards to quantum computing. I'm hoping we're at least as stringent about these experiments. But so far, I've only ever seen them done in open-air environments, which to me leaves too many nagging questions. I doubt the quantum effects I can produce in my dusty office are as precise and pure as they would be in a proper lab, but all the evidence I've seen is that I'm doing it pretty much precisely the same (sloppy) way. Electrons do indeed show the same effect and I recall reading once that the experiment was first proposed using electrons. There are other particle/wave effects as well, but those two are the easiest to demonstrate with, apparently.
  - gus_massa 7y ago
    > We speak of "noise" (interference) Note that interference here has a very technical meaning that is NOT noise. (Sorry for the all-caps, but it's very important in these experiments.) I think you don't understand the important point in the double slit experiment. Let's try to explain it, but it's a long explanation. --- First you must understand the single slit experiment. If the slit is thin enough you get a nice diffraction patter. If this spread was caused by dust or something like that, a good guess is that the image gets a gaussian blur like exp(-x^2). In a diffraction experiment, the image you get is something like sin²(x)/x². (You should draw them in Wolfram Alpha or something.) The main difference is that the first one is always positive, so you get light everywhere, but it get's dimmer very soon. The second one has a lot of zeros, so you get strips of light and darkness. The math details are complicated, so let's ignore them. You can do this experimentally. In the lab we used two razorblades with some screws to move them arcuately. There should be plenty of recipes in Internet to reproduce it. You can try it in more dusty environments, and clean environment. Sharp razorblades, not sharp razorblades. Wind or not wind. Try it a few times until you get use to the images it produces. You will notice that the cleaner environment produce the better results, so I hope you will get convinced that it's not caused by the dust or something You can probably buy some single slit from an educational provider. Buy some of them of different width to compare the results with your homemade version. It's important to understand how it looks before going to the second step, so play for some time with the single slit version. Some resources: https://en.wikipedia.org/wiki/Diffraction#Single-slit_diffraction https://en.wikipedia.org/wiki/Diffraction#Single-slit_diffra... --- Now, the double slit version looks more difficult to make at home. I think you should buy one (or a few), and the single slit version with the same width. The idea is that if it has only one slit you would see the old image. If you have only the other slit you would see the old image. If the screen is far away and the slits are very close, you can't notice the difference. So you would expect to see the same image, but with more bright. The weird thing is that you don't get the same image. You get almost the same image but with a lot of additional strips. There are the old dark lines and many new dark lines. These new dark lines are the interesting one. In this lines you have something like . light + light = darkness Try the experiment in air and try to read the explanations in https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/Double-slit_experiment and https://www.youtube.com/watch?v=Iuv6hY6zsd0 https://www.youtube.com/watch?v=Iuv6hY6zsd0 . Try again until you scream <all-caps> "The new dark lines are weird!"</all-caps> If you are not screaming, try the experiments with one and two slits again and the info again. You can try with a dusty windy environment, and it should make the lines more fuzzy. You can try wit a clean environment and get better results. The lines are not caused by the dust, they are just weird. . light + light = darkness (If you are going to buy things, add a diffraction gratting. It's like using many slits instead of two. The math is more difficult but they create nice rainbows. https://en.wikipedia.org/wiki/Diffraction_grating https://en.wikipedia.org/wiki/Diffraction_grating ) The dark lines are not so surprising when you use light that is usually approximated a wave. But if you get more advanced equipment you can repeat the same experiment with electrons or neutrons and get the same weird lines. (When you understand this, you can scream again.)

by ksaj 7y ago

gus_massa 7y ago

> Has the double slit experiment been done and verified in a vacuum? 99.9999999% sure yes, but I can't find a source with the actual experiment. The versions with electrons are made in vacuum, but I'm not sure they use the double slit pattern. You can reproduce the experiment with light in air. It's expected that you will get the same result in vacuum. An actual experiment is nice, but the setup in more complicated, so it's not done in a normal lab class. It should be easy to setup for someone with access to a vacuum pump, and some free time (1 week top). It would be nice to see how the lines move when the refraction index of the air that is almost 1 changes to the refraction index of vacuum that is exactly 1. It's hard to convince someone of doing the actual experiment, because it looks a lot of work without an insightful result. Perhaps you are lucky and someone already did this. I guess this is the case, but I can't find it. Perhaps you can convince someone like Cody of "Cody's lab" to make the experiment and upload a video.

ksaj 7y ago
Exactly. Lots of food for thought there. I expect these results in the open air, since there is so much for the photons to bounce off of. They're probably even bouncing off the sides of the actual slits, unless the block is thin and precise enough, and anti-reflective enough to not allow light bouncing off of it - straight polarized lines only. This is why I ask such a specific question. I don't deny the effect is happening at all - I question the influence of other parts not taken care of in the experiment. We speak of "noise" (interference) when discussing related observations in regards to quantum computing. I'm hoping we're at least as stringent about these experiments. But so far, I've only ever seen them done in open-air environments, which to me leaves too many nagging questions. I doubt the quantum effects I can produce in my dusty office are as precise and pure as they would be in a proper lab, but all the evidence I've seen is that I'm doing it pretty much precisely the same (sloppy) way. Electrons do indeed show the same effect and I recall reading once that the experiment was first proposed using electrons. There are other particle/wave effects as well, but those two are the easiest to demonstrate with, apparently.
- gus_massa 7y ago
  > We speak of "noise" (interference) Note that interference here has a very technical meaning that is NOT noise. (Sorry for the all-caps, but it's very important in these experiments.) I think you don't understand the important point in the double slit experiment. Let's try to explain it, but it's a long explanation. --- First you must understand the single slit experiment. If the slit is thin enough you get a nice diffraction patter. If this spread was caused by dust or something like that, a good guess is that the image gets a gaussian blur like exp(-x^2). In a diffraction experiment, the image you get is something like sin²(x)/x². (You should draw them in Wolfram Alpha or something.) The main difference is that the first one is always positive, so you get light everywhere, but it get's dimmer very soon. The second one has a lot of zeros, so you get strips of light and darkness. The math details are complicated, so let's ignore them. You can do this experimentally. In the lab we used two razorblades with some screws to move them arcuately. There should be plenty of recipes in Internet to reproduce it. You can try it in more dusty environments, and clean environment. Sharp razorblades, not sharp razorblades. Wind or not wind. Try it a few times until you get use to the images it produces. You will notice that the cleaner environment produce the better results, so I hope you will get convinced that it's not caused by the dust or something You can probably buy some single slit from an educational provider. Buy some of them of different width to compare the results with your homemade version. It's important to understand how it looks before going to the second step, so play for some time with the single slit version. Some resources: https://en.wikipedia.org/wiki/Diffraction#Single-slit_diffraction https://en.wikipedia.org/wiki/Diffraction#Single-slit_diffra... --- Now, the double slit version looks more difficult to make at home. I think you should buy one (or a few), and the single slit version with the same width. The idea is that if it has only one slit you would see the old image. If you have only the other slit you would see the old image. If the screen is far away and the slits are very close, you can't notice the difference. So you would expect to see the same image, but with more bright. The weird thing is that you don't get the same image. You get almost the same image but with a lot of additional strips. There are the old dark lines and many new dark lines. These new dark lines are the interesting one. In this lines you have something like . light + light = darkness Try the experiment in air and try to read the explanations in https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/Double-slit_experiment and https://www.youtube.com/watch?v=Iuv6hY6zsd0 https://www.youtube.com/watch?v=Iuv6hY6zsd0 . Try again until you scream <all-caps> "The new dark lines are weird!"</all-caps> If you are not screaming, try the experiments with one and two slits again and the info again. You can try with a dusty windy environment, and it should make the lines more fuzzy. You can try wit a clean environment and get better results. The lines are not caused by the dust, they are just weird. . light + light = darkness (If you are going to buy things, add a diffraction gratting. It's like using many slits instead of two. The math is more difficult but they create nice rainbows. https://en.wikipedia.org/wiki/Diffraction_grating https://en.wikipedia.org/wiki/Diffraction_grating ) The dark lines are not so surprising when you use light that is usually approximated a wave. But if you get more advanced equipment you can repeat the same experiment with electrons or neutrons and get the same weird lines. (When you understand this, you can scream again.)