Question about single slit diffraction

[Doc Al]

Thus in both the single slit case and the double slit and multiple slit cases I would not expect the alternating pattern of light and dark stripes etc to occur if their is a vacuum in the space between the slits.

Why not just try it and see? Go to the nearest High School or College physics department--any place with a bell jar, vacuum pump, and laser would do--and ask them to set it up. (Or do it yourself, if you have access to a lab.) A bell jar isn't exactly high vacuum, but you should be able to reduce the air pressure by a factor of 100 or so. That should be enough.

 

[rob5]

Why stop at 2-slit? Why not also say that multi-slit inteference such as from a diffraction grating is also not detected in vacuum?


I said that it applies to multislits. The question is about the need for molecules of air or something, as in an xray crystal, between the slits.
The light source acts on these molecules between the slits after a delay which is greater for points further from the source and at points one period greater there is in phase addition and at points half a period greater there is out of phase cancellation of the influence of light.
The same thing applies to the points of the image wall or screen beyond the slit or slits and that produces the alternating bright and dark stripes or spots.
Now suppose you do a single slit diffractions experiment in a partial vacuum and you find there is no such diffraction pattern but rather a pattern that suggests light moved from the source to the image wall or screen in a straight line.
Then as you add more air to the partial vacuum you find that a diffraction pattern becomes more and more evident.
The conclusion would be that light can move in a vacuum but cannot move as a wave(having the interference properties of waves) unless there is a material medium.
But this experiment has never been done.

 

[ZapperZ]

Why stop at 2-slit? Why not also say that multi-slit inteference such as from a diffraction grating is also not detected in vacuum?


I said that it applies to multislits. The question is about the need for molecules of air or something, as in an xray crystal, between the slits.
The light source acts on these molecules between the slits after a delay which is greater for points further from the source and at points one period greater there is in phase addition and at points half a period greater there is out of phase cancellation of the influence of light.
The same thing applies to the points of the image wall or screen beyond the slit or slits and that produces the alternating bright and dark stripes or spots.
Now suppose you do a single slit diffractions experiment in a partial vacuum and you find there is no such diffraction pattern but rather a pattern that suggests light moved from the source to the image wall or screen in a straight line.
Then as you add more air to the partial vacuum you find that a diffraction pattern becomes more and more evident.
The conclusion would be that light can move in a vacuum but cannot move as a wave(having the interference properties of waves) unless there is a material medium.
But this experiment has never been done.

Terrific! Now we have finally the ultimate admission of ignorance.

May I suggest that you visit the SAME synchrotron facilities that I have suggested, and asked them how a "monochromator" works. Then ask them where they placed this device. After you've convinced yourself, then look at their inteferometer, their diffractometer, and the rest of the devices along the vacuum beamlines.

My guess is, you won't. But I would LOVE to be proven wrong here. You appear to not want to make ANY effort to double check your claim, even after I've given you a source to go look. There are plenty of evidence. You are just ignorant of them.

Zz.

 

[rob5]

Terrific! May I suggest that you visit the SAME synchrotron facilities that I have suggested, and asked them how a "monochromator" works. Then ask them where they placed this device. After you've convinced yourself, then look at their inteferometer, their diffractometer, and the rest of the devices along the vacuum beamlines.

If you know how these things work, then you probably know that they are not vacuous and molecules in these devices contain oscillating charged particles. The evacuated tubes containing electron beams are something else.
You said in a previous post that I should do this experiment because it is so easy to do with a small bell jar vacuum. I don't think so. I saw a company,Abesse, that made a 4ft by 4ft by 5ft and possibly tubes that would be 10 ft by 1 ft by 1ft which would be better to duplicate the typical single slit, of a few mm, diffraction experiment with visible light.
The point is that it can be done but that it has never been done. And therefore that the single slit and double slit diffraction experiments do not prove that light moves as a wave in a vacuum.

 

[ZapperZ]

Terrific! May I suggest that you visit the SAME synchrotron facilities that I have suggested, and asked them how a "monochromator" works. Then ask them where they placed this device. After you've convinced yourself, then look at their inteferometer, their diffractometer, and the rest of the devices along the vacuum beamlines.

If you know how these things work, then you probably know that they are not vacuous and molecules in these devices contain oscillating charged particles. The evacuated tubes containing electron beams are something else.
You said in a previous post that I should do this experiment because it is so easy to do with a small bell jar vacuum. I don't think so. I saw a company,Abesse, that made a 4ft by 4ft by 5ft and possibly tubes that would be 10 ft by 1 ft by 1ft which would be better to duplicate the typical single slit, of a few mm, diffraction experiment with visible light.
The point is that it can be done but that it has never been done. And therefore that the single slit and double slit diffraction experiments do not prove that light moves as a wave in a vacuum.

First of all, it was doc al who suggested it, not me.

Secondly, "oscillating molecules in these devices"?

You have shifted your position so often, it is no longer clear WHAT you are claiming. You first claim that only the single slit hasn't been done in vacuum, after I pointed out how they select the frequency of light to use. Then when I point out that it is way too easy to show the single-slit diffraction pattern simply based on the modulations of the intensity of the interference slit, you now are claiming that ALL interference effects have not been seen in vacuum.

And now, without even bothering to figure out what a monochromator is, how it works, and what exactly it produces, you have already dismissed it. Keep in mind, you are doing this without a SINGLE quantitative model that uses your "guesses" to that this cannot happen in vacuum, etc.

I recommend that this thread go into the TD section where, hopefully, it'll meet with a quick death.

Zz.

 

[rob5]

Secondly, "oscillating molecules in these devices"?
You have shifted your position so often,

1) I am just responding to your shift in focus to xray crystal diffraction from single slit and double slit diffraction. In all of these cases the light passes through some sort of molecules, those of the crystal or those of air.

It is no longer clear WHAT you are claiming.

2) Evidently we both agree now that neither single nor double slit diffraction has be shown in a vacuum and now that xrays from a synchroton have not been diffracted in a vacuum since a crystal is not a vaccum.
Therefore there is no direct evidence that light travels as a wave with the interference properties of a wave, in a vacuum even though as Michelson et al showed in 1915 after Michelson's death that light somehow travels in a vacuum at a speed very close to its speed in air.