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Variation of ‘two-slit’ experiment
Posted: 28 September 2007 01:36 PM   [ Ignore ]
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All,

After reading a related article in Newscientist, i came up with a variation of the ‘two slit’ experiment. I have had a rummage around t’internet and havent found anything similar, so I thought some of the ‘nerdy types’ (you know who you are wink ) on here may be able to help.

see attached image. Basically, the surface on which we would expect to see the interference pattern, is ‘faceted’ so that each facet only faces one of the slits. that is, the surface is an extended ‘saw-tooth’ type pattern. Clearly the height of the ‘teeth’ must be significantly less than that wavelength of the light for this to be valid. This arrangement will identify which slit the photon came from, which must therefore destroy the interference pattern. The experiment gets more interesting if only half of the surface has the saw-tooth pattern. if the lower half of the area where the interference pattern falls is smooth as in the original experiment, we should see two bright bands on the upper area and the interference pattern on the lower area…......or should we??

This is such a simple experiment that i cannot believe it hasn’t been done before. If it has been done, what was the result and if it hasn’t, what do we predict will happen?

If it does work as i believe it will, it would make a great demonstration of the weirdness of ‘the world of the very small’.

SkiCarver.

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Posted: 28 September 2007 01:42 PM   [ Ignore ]   [ # 1 ]
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SkiCarver - 28 September 2007 01:36 PM

All,

After reading a related article in Newscientist, i came up with a variation of the ‘two slit’ experiment. I have had a rummage around t’internet and havent found anything similar, so I thought some of the ‘nerdy types’ (you know who you are wink ) on here may be able to help.

see attached image. Basically, the surface on which we would expect to see the interference pattern, is ‘faceted’ so that each facet only faces one of the slits. that is, the surface is an extended ‘saw-tooth’ type pattern. Clearly the height of the ‘teeth’ must be significantly less than that wavelength of the light for this to be valid. This arrangement will identify which slit the photon came from, which must therefore destroy the interference pattern. The experiment gets more interesting if only half of the surface has the saw-tooth pattern. if the lower half of the area where the interference pattern falls is smooth as in the original experiment, we should see two bright bands on the upper area and the interference pattern on the lower area…......or should we??

This is such a simple experiment that i cannot believe it hasn’t been done before. If it has been done, what was the result and if it hasn’t, what do we predict will happen?

If it does work as i believe it will, it would make a great demonstration of the weirdness of ‘the world of the very small’.

Great thinking ... I have no idea if it’s been done. If I were you I’d check out Richard Feynman’s Six Easy Pieces, which has a chapter on quantum mechanics where he discusses the two-slit experiment. The long and short of it is that any time you set the experiment up so that you can TELL which of the two slits the light went through, you no longer get the interference patterns. But IIRC he doesn’t discuss the option you bring up. We’d need a good physicist here to tell us if it’s been tried or not.

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Posted: 28 September 2007 02:15 PM   [ Ignore ]   [ # 2 ]
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DS,

I have read RPF’s books and I do not recall seeing this arrangement. It would be very interesting to see if you get both the two bright bands AND the interference pattern in the same experiment. it would be simple to construct, so if it does work, it would be a great high school demonstration.

Maybe I should look up some university physics professor types and email it to them.

Ski.

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Posted: 28 September 2007 02:32 PM   [ Ignore ]   [ # 3 ]
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RAmen, brother!

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Posted: 28 September 2007 02:40 PM   [ Ignore ]   [ # 4 ]
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truthaddict - 28 September 2007 02:32 PM

RAmen, brother!

miso RAmen to you!

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Posted: 28 September 2007 03:00 PM   [ Ignore ]   [ # 5 ]
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This website gives a nice interactive highschool understanding of this principle.

http://www.colorado.edu/physics/2000/schroedinger/index.html

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Posted: 28 September 2007 03:15 PM   [ Ignore ]   [ # 6 ]
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Retrospy,

I found that site when I looked for the configuration I came up with. I found many sites which had good explainations of the ‘classic two-slit’ experiment, and even ones with mention of light sensors so we could determine which slit the photon went through, and how that collapsed the intereference pattern. no site I found showed anything like the ‘SkiCarver setup’!! if you can point us to a site which does show something similar i would appreciate it.

Ski.

edited for carp speeling

[ Edited: 28 September 2007 03:57 PM by SkiCarver ]
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Posted: 28 September 2007 03:53 PM   [ Ignore ]   [ # 7 ]
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We need to get Victor Stenger here ... he’d probably be able to answer the question. I’ll see if I can. Fingers crossed.

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Posted: 28 September 2007 10:04 PM   [ Ignore ]   [ # 8 ]
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I haven’t seen narwhol around lately, but he’d probably be a good person to evaluate this.

Occam

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Posted: 29 September 2007 12:54 PM   [ Ignore ]   [ # 9 ]
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SkiCarver - 28 September 2007 01:36 PM

All,

After reading a related article in Newscientist, i came up with a variation of the ‘two slit’ experiment.

Can you give us your reference.  (it looks like NewScientist WWW site is down Sat am)

Here are some related ones:
[metanexus.net link] Antony Valentini—this is an example of people re—looking at the double slit experiment.  There is a smaller Feynman book mentioned here QED—The strange Theory of Light and Matter[LINK]  which ‘focuses’ on this topic of waves vs. particles.

 

Physics World Mar 2005 article on double slit experiment [LINK] including work at Texas A&M.

The Double Slit Experiement has been called “the most beautiful experiment” [ Physics World Sept 2002]  

There seems to be a lot of work on double slits so I’m not sure which work is being referred to.

In regard to this proposed expt, one needs to try it.

[ Edited: 29 September 2007 07:01 PM by Jackson ]
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Posted: 29 September 2007 05:14 PM   [ Ignore ]   [ # 10 ]
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Jackson, to make it easier to read your posts, close the quoted section with [ / q u o t e ] (without the spaces) and it will display properly. I could edit these myself, but I’d prefer if you do it.

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Posted: 29 September 2007 06:07 PM   [ Ignore ]   [ # 11 ]
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Clearly the height of the ‘teeth’ must be significantly less than that wavelength of the light for this to be valid.

  This may be the hang-up.  An angstrom is one hundred-millionth of a centimeter, and I believe visible light is measured in the hundreds of angstroms.  The height of the teeth would be so small that one would almost certainly not be able to construct such a device.

Occam

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Posted: 01 October 2007 02:53 PM   [ Ignore ]   [ # 12 ]
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Here’s the response I got from Victor Stenger. Not sure if it quite clears the case up, but food for thought anyhow.


[quote author=“Victor Stenger”]Anything you do to detect which slit the photon goes through will destroy the interference pattern. But why should you expect one? When you change an experiment you should expect different results.

Note that the interference pattern in the two slit experiment is not for individual photons but is just the probability distribution of an ensemble of photons. Photons are not waves,  they are particles. The only wave is the wave function which gives the probability distribution and this is a mathematical abstraction, not a reality.

I have written much on this. See my web page

http://www.colorado.edu/philosophy/vstenger/meta.html

and a recent Skeptical Briefs column at

http://www.colorado.edu/philosophy/vstenger/Briefs/Mindless.doc

Vic

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Posted: 01 October 2007 05:28 PM   [ Ignore ]   [ # 13 ]
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Huh???  confused

Occam

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Posted: 01 October 2007 05:59 PM   [ Ignore ]   [ # 14 ]
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Occam - 01 October 2007 05:28 PM

Huh???  confused

Occam

Occam,

I fully agree. I really do not understand what VS was saying there.

 

I guess the point i was trying to make is that it will be a simple demo which will easily show both the interference pattern and the two bright bands where the pattern is destroyed by the ‘saw-teeth’. This will happen regardless of the size of the ‘teeth’. I believe this would be a great demo for highlighting the quantum weirdness. that is, unless my ignorance is getting the better of me!

Ski.

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Posted: 01 October 2007 08:12 PM   [ Ignore ]   [ # 15 ]
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dougsmith - 29 September 2007 05:14 PM

Jackson, to make it easier to read your posts, close the quoted section with [ / q u o t e ] (without the spaces) and it will display properly. I could edit these myself, but I’d prefer if you do it.

big surprise
thanks thsee aer just tpyos grin

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