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Variation of ‘two-slit’ experiment
Posted: 01 October 2007 09:40 PM   [ Ignore ]   [ # 16 ]
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Skicarver, I think you missed the point of my earlier post.  The teeth would be only a few molecules high so there would be no way to see what was going on.  In other words, while your concept may have been valid (although I believe V.S. stated that it wasn’t), the experimental design can’t be accomplished. 

Occam

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Posted: 02 October 2007 01:24 PM   [ Ignore ]   [ # 17 ]
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Occam - 01 October 2007 09:40 PM

Skicarver, I think you missed the point of my earlier post.  The teeth would be only a few molecules high so there would be no way to see what was going on.  In other words, while your concept may have been valid (although I believe V.S. stated that it wasn’t), the experimental design can’t be accomplished. 

Occam

i had a few more thoughts on that whole wavelength thing.

1. the wave function would still be destroyed by the ‘teeth’ even if the teeth are many times the wavelength of the light.

2. if the distance between the peaks was less than the wave length of the light, the surface would be effectively smooth as far as the light is concerned. that was a mistake on my part.  the ‘normal’ interference pattern would be seen.

3. I may be interested in the subject of quamtum mechanics, but i clearly have no idea what i’m talking about!!  If the root of wisdom is being able to say “i don’t know” then i must be really wise, ‘cause “I don’t know squat!”

Ski.

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Posted: 02 October 2007 04:15 PM   [ Ignore ]   [ # 18 ]
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What you need is a good physics instructor who can give you the guidelines as to what you should learn so you can recognize whether your experiment is sensible, not a research physicist who just says it’s wrong and rattles off some esoteric scientific rules.

Occam

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Posted: 02 October 2007 05:02 PM   [ Ignore ]   [ # 19 ]
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Occam - 02 October 2007 04:15 PM

What you need is a good physics instructor who can give you the guidelines as to what you should learn so you can recognize whether your experiment is sensible, not a research physicist who just says it’s wrong and rattles off some esoteric scientific rules.

Occam

i will try to find a local university with a physics department and hassle them until I get a good answer!

Ski

p.s. ta for the comments guys!

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Posted: 04 October 2007 12:32 AM   [ Ignore ]   [ # 20 ]
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OOOH!  QM is onne of my very most favoritest topics in the whole world ever and stuff!  I get so excited, my grammar goes to poo.

It’s been a few years since I did any QM study, but I’ll give this one a go!

You have a nice idea for an experiment, but let’s look at its most essential features:

1) Partial coverage of the “impact area” of photons against a screen (say, a photographic plate) by a directionally sensitive set of detectors.

2) It is sufficient to detect if a given photon came from ONE of the slits, for if it did not, it must have come from the other.  Your detector is simply a means of determining trajectory direction, rather than simply incidence (or *splat*) location.

3) Full coverage of the detector area would correspond to having a single detector closer to one of the slits.

Quantum mechanics tells us (or at least quantum mechanicists tell us, or write to us, or have their people tell our people) that you cannot know both the position and the motion of a quantum thingy with simultaneous arbitrary precision.  Similarly, an entity cannot exhibit particle-like and wave-like pheonomena simultaneously vis-a-vis its interactions with the universe (or, specifically in interactions with an observer). 

One of my favorite explanatory frameworks for the Young double-slit experiment is electron interference.  Since elctrons have charge, they can be measured more easilly then photons - yet their duality makes experiments with them qualitatively identical to those with photons.

Imagine eletrons passing through a double-slit screen.  We can put an itsy-bitsy metal loop just in front of one of the slits, and thus detect when an electron exits that slit.  When this is done (and in essense, it has been done), the interference pattern on the whole screen vanishes, and one gets two dogpiles of electrons from the two slits rather than interference bands.  If one takes away the itsy-bitsy metal loop, the interference pattern returns.  This happens even if the other slit is left unattended (un-detected).

Your directional detector seems to me to take the place of the itsy-bitsy metal loop.  Assuming it can determine that a photon came through one slit or the other (though the notion of “determine” is a bit loose here), it would “cause” the interference pattern to vanish for the entire viewing screen or target area.

This leads me to think about one of the coolest things I learned:  If you send one photon (or electron, or neutron, etc.) at a time through the slits, over time an interference pattern will show up, even though each “particle” causes just one little *splat* on the detector screen.  Put a itsy-bitsy loop in, and the pattern vanishes.  It’s as if the particles “talk” through time.  Such time-independent correlation behavior spooks the heebie-jeebies out of a lot of phsyicists, from a metaphisical standpoint.  It’s been a cause of such wild ideas as the “many-worlds” theory, and nonlocality (e.g. trans-luminal signaling).

I have some of my own crack-brained notions about how to interpret the whole ball of cookies, but that’s going too far afiled for the time being.

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Posted: 22 October 2007 02:14 AM   [ Ignore ]   [ # 21 ]
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SkiCarver:

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.

Why do you think this arrangement will identify which slit a photon comes from?

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Posted: 22 October 2007 05:05 PM   [ Ignore ]   [ # 22 ]
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jr,

it would identify the slit because the facet is only visible from one slit so the photon cannot travel from the other slit.

Ski.

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Posted: 24 October 2007 03:43 AM   [ Ignore ]   [ # 23 ]
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SkiCarver - 22 October 2007 05:05 PM

it would identify the slit because the facet is only visible from one slit so the photon cannot travel from the other slit.

For this to work, it seems to me that the slits would need to be infinitely narrow.

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Posted: 13 November 2007 11:09 AM   [ Ignore ]   [ # 24 ]
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For news of a recent “two-slit” experiment:  http://www.sciencedaily.com/releases/2007/11/071109090639.htm

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