| Topic: |
Science > Physics |
| User: |
"GeordieSi" |
| Date: |
09 Feb 2006 01:19:03 PM |
| Object: |
Double slit experiment confusion |
Hi All. Maybe another daft question but I'm troubled by the double-slit
experiment used to demonstrate 'wave-particle duality'. I recognise
that I don't know all the different versions of QM theory but how can a
photon's wave component interfere with itself. In the standard
presentation a light source is shone through a set of slits (presumably
a diffraction grating in practice) onto a detector at the back. If I
imagine placing the detector say to the left of centre behind the
'slits' then assuming that light has a finite speed then the photon
wave will take longer to reach the detector from the right slit than
the left. If they don't reach at the same time how can they interfere
(assuming we reduce the light intensity so that only one photon passes
each time). If the wave is somehow standing rigid (a) how can it all
collapse instantaneously and (b) how can the photon be said to be
moving (as in relativity). I hesitate to show my ignorance but I'd
rather know than not.
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| User: "RP" |
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| Title: Re: Double slit experiment confusion |
21 Feb 2006 10:37:42 PM |
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GeordieSi wrote:
Hi All. Maybe another daft question but I'm troubled by the double-slit
experiment used to demonstrate 'wave-particle duality'. I recognise
that I don't know all the different versions of QM theory but how can a
photon's wave component interfere with itself.
Absorption and emission. The wave interacts with the charges in the slit
material producing secondary waves. The primary and secondary waves all
interfere with each other.
In the standard
presentation a light source is shone through a set of slits (presumably
a diffraction grating in practice) onto a detector at the back. If I
imagine placing the detector say to the left of centre behind the
'slits' then assuming that light has a finite speed then the photon
wave will take longer to reach the detector from the right slit than
the left. If they don't reach at the same time how can they interfere
(assuming we reduce the light intensity so that only one photon passes
each time).
Seems you've located the error already. The obvious conclusion is that
one em wave at a time simply doesn't occur. Even when the controlled
source is turned off it will still be emitting radiation, as will the
entire universe of matter around it. Even the detector is producing
radiation. In so-called one-photon-at-a-time experiments it is
photoemission events that are being counted, not photons. Nice twist on
the argument BTW.
If the wave is somehow standing rigid (a) how can it all
collapse instantaneously
It doesn't collapse at all. It continues to propagate outward,
spherically, for as long as it has space to propagate into.
Along the way it interferes with charges, that in turn produce secondary
radiation that interferes destructively with it.
and (b) how can the photon be said to be
moving (as in relativity).
Photons are just spherical em waves emitted by atoms/molecules as they
undergo transitions between energy levels.
I hesitate to show my ignorance but I'd
rather know than not.
You won't find any satisfactory standard answer to your question. Your
observation is sufficient in itself to destroy the photon model of light
propagation.
Richard Perry
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| User: "GeordieSi" |
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| Title: Re: Double slit experiment confusion |
22 Feb 2006 04:23:06 PM |
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Thanks for all the comments. I reckon I have got a long way to go
before I understand this experiment. I'm not sure if I am using
misleading terminology so I'll try and keep myself in check during this
post.
Richard, are you arguing that it is impossible to ensure that there is
only one photon (quantum) in the system at any one time and that the
interference fringes are formed from multiple photons passing through
the slits simultaneously? Or are you just pointing out that the concept
of particulate photons (compact size) is outdated and waves are much a
more appropriate concept?
If we consider the experiment entirely as em waves I seem to run up
against troubling questions. How long must these waves be? If they
propagate in every direction then why does each wave only produce one
absorption event (how can the wave collapse instantaneosly to prevent
such multiple absorptions?). Also how do these waves propagate? Do the
'peaks' move along (like a water wave) or are they fixed in space (an
undulating front moves ahead)?
I guess these questions might be answered if I picked up a book on
electromagnetism but any help would be appreciated.
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| User: "RP" |
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| Title: Re: Double slit experiment confusion |
22 Feb 2006 05:48:36 PM |
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GeordieSi wrote:
Thanks for all the comments. I reckon I have got a long way to go
before I understand this experiment. I'm not sure if I am using
misleading terminology so I'll try and keep myself in check during this
post.
Richard, are you arguing that it is impossible to ensure that there is
only one photon (quantum) in the system at any one time and that the
interference fringes are formed from multiple photons passing through
the slits simultaneously? Or are you just pointing out that the concept
of particulate photons (compact size) is outdated and waves are much a
more appropriate concept?
If we consider the experiment entirely as em waves I seem to run up
against troubling questions. How long must these waves be? If they
propagate in every direction then why does each wave only produce one
absorption event (how can the wave collapse instantaneosly to prevent
such multiple absorptions?). Also how do these waves propagate? Do the
'peaks' move along (like a water wave) or are they fixed in space (an
undulating front moves ahead)?
I guess these questions might be answered if I picked up a book on
electromagnetism but any help would be appreciated.
Yes, I'm arguing that photons aren't particles and that you cannot
achieve one photon at a time, even when the photon is properly
interpreted as a spherically expanding retarded wave.
If you examine the devices sold for the purpose of counting photons
you'll find that the photocathode is pumped. Only slight disturbances of
the appropriate frequency are required to get the electrons over the
potential hill represented by the work function. One photoemission event
at a time occurs as a result of the light source, which can be
discriminated from the background noise. However, the source emission
events aren't being counted, they are only assumed to correspond
one-to-one with the measured photoemission events at the photocathode.
When you approach em radiation from the perspective of long wavelengths,
such as in radio transmissions, then the one-electron detection of em
waves becomes a bit nonsensical. The entire electron population in the
transmitting antenna is involved in the generation of em waves at these
frequencies, and likewise the electrons in the receiving antenna work in
conjunction to absorb energy from the ambient field.
Lensing is a good example in the micro-realm of wave mechanics in
action. The point-photon cannot possibly propagate through all of the
lens material simultaneously, this requires a wave. Probability waves
may work on paper, but waves are waves. If they have a real physical
influence on electrons, then we are speaking of the same waves albeit in
different terms, and photons are redundant.
The universe is awash with ambient radiation of all frequencies. The
idealistic idle metallic surface of Einstein's photoelectric argument is
the problem. Work function is nothing other than the energy required to
remove an electron from the surface.
There are however several electrons doing so without the light source
turned on. The micro-realm is a busy place, very chaotic.
Turning the light on increases the number of photoelectrons in
proportion of the energy of the emitted light. This is just conservation
of energy. The incident energy on the surface that doesn't go toward
removing electrons goes toward heating the surface. The phonons created
in turn pump the surface. In this way the excess light energy eventually
finds its way to the emitted electrons.
One prediction of this model is that the photocathode current will not
instantly rise to peak upon turning on the light source.
The surface will require some brief time to stabilize.
Richard Perry
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| User: "GeordieSi" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 12:01:18 PM |
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Very interesting. I'd pretty much come to the conclusion that it is
best to think of everything as waves. I can see the problems of trying
to explain clearly complex processes with very simple models but I've
been trying to imagine what properties such probability waves might
have. I seem to run into problems when I use a fixed speed of light in
the quantum model. I have a few naive (again) questions.
Firstly I'd read some popular works on QED by Feynman. The sum over
histories approach seems to imply a variable speed of light (I'm
probably wrong about that).
Secondly, once when a wave is absorbed by an electron (which I guess is
also a wave) it must 'collapse' instantly otherwise I presume there
would be problems with the left over portion interacting with other
things. However it would seem that this collapse would need to be
faster than the speed of light.
Thanks again.
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| User: "Spaceman" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 12:12:49 PM |
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"GeordieSi" <simon@hopkins9666.fsbusiness.co.uk> wrote in message
news:1141840878.556515.170480@z34g2000cwc.googlegroups.com...
Very interesting. I'd pretty much come to the conclusion that it is
best to think of everything as waves. I can see the problems of trying
to explain clearly complex processes with very simple models but I've
been trying to imagine what properties such probability waves might
have. I seem to run into problems when I use a fixed speed of light in
the quantum model. I have a few naive (again) questions.
You should run into problems using a constant speed of light
since to be able to always have a constant speed of light
you need to have a transform and allow length and time to no longer
be constants and that would just plain be silly.
(like using rubber rulers and bad timers.)
:)
Firstly I'd read some popular works on QED by Feynman. The sum over
histories approach seems to imply a variable speed of light (I'm
probably wrong about that).
You are not wrong.
Light always traveling at c to all observers is an ignorance of relative
speed
differences.
The only mathematical proof they have for constant to all observer
lightspeed is a silly self limiting mathematical trick called a transform.
Secondly, once when a wave is absorbed by an electron (which I guess is
also a wave) it must 'collapse' instantly otherwise I presume there
would be problems with the left over portion interacting with other
things. However it would seem that this collapse would need to be
faster than the speed of light.
A light wave would collapse faster for things moving towards the light
source
and slower for things moving away from the lightsource.
--
James M Driscoll Jr
Spaceman
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| User: "Greg Neill" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 12:38:52 PM |
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"Spaceman" <Realspace@comcast.not> wrote in message
news:wMWdnZ8kjtEFg5LZnZ2dnUVZ_v-dnZ2d@comcast.com...
[nothing based upon empirical fact]
Pay no attention to Spacimen. He's a science
illiterate.
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| User: "Spaceman" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 01:02:36 PM |
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"Greg Neill" <gneillREM@OVE.THIS.netcom.ca> wrote in message
news:9wFPf.2345$xM2.161129@news20.bellglobal.com...
"Spaceman" <Realspace@comcast.not> wrote in message
news:wMWdnZ8kjtEFg5LZnZ2dnUVZ_v-dnZ2d@comcast.com...
[nothing based upon empirical fact]
Pay no attention to Spacimen. He's a science
illiterate.
Poor Greg,
He hates the fact that he needs a transform to mathematically
prove constant lightspeed for all observers..
He must know that a transform should not be needed if light
speed were actually constant for all observers..
LOL
--
James M Driscoll Jr
Spaceman
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| User: "Sam Wormley" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 01:08:09 PM |
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Spaceman wrote:
"GeordieSi" <simon@hopkins9666.fsbusiness.co.uk> wrote in message
news:1141840878.556515.170480@z34g2000cwc.googlegroups.com...
Very interesting. I'd pretty much come to the conclusion that it is
best to think of everything as waves. I can see the problems of trying
to explain clearly complex processes with very simple models but I've
been trying to imagine what properties such probability waves might
have. I seem to run into problems when I use a fixed speed of light in
the quantum model. I have a few naive (again) questions.
You should run into problems using a constant speed of light
since to be able to always have a constant speed of light
you need to have a transform and allow length and time to no longer
be constants and that would just plain be silly.
(like using rubber rulers and bad timers.)
:)
Spitshit, Spaceshit, Spaceman, or whatever you call the little
troll has quite the track record and is a registered crank at
crank dot net.
http://www.google.com/search?q=Spaceman+site%3Awww.crank.net
For a few laughs try the Spaceman [spaceshit] Emulator
http://www.hyperdeath.co.uk/spaceman/
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| User: "Spaceman" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 01:10:11 PM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:tYFPf.11764$oL.2693@attbi_s71...
Spaceman wrote:
"GeordieSi" <simon@hopkins9666.fsbusiness.co.uk> wrote in message
news:1141840878.556515.170480@z34g2000cwc.googlegroups.com...
Very interesting. I'd pretty much come to the conclusion that it is
best to think of everything as waves. I can see the problems of trying
to explain clearly complex processes with very simple models but I've
been trying to imagine what properties such probability waves might
have. I seem to run into problems when I use a fixed speed of light in
the quantum model. I have a few naive (again) questions.
You should run into problems using a constant speed of light
since to be able to always have a constant speed of light
you need to have a transform and allow length and time to no longer
be constants and that would just plain be silly.
(like using rubber rulers and bad timers.)
:)
Spitshit, Spaceshit, Spaceman, or whatever you call the little
troll has quite the track record and is a registered crank at
crank dot net.
http://www.google.com/search?q=Spaceman+site%3Awww.crank.net
For a few laughs try the Spaceman [spaceshit] Emulator
http://www.hyperdeath.co.uk/spaceman/
Attack the poster when you have no attack for the post itself.
Good Work Sam Wormley, worshipper of SR.
:)
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| User: "G=EMC^2 Glazier" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 02:33:47 PM |
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Sam Best to think that all particles move in pairs staying parrel to
each other. That takes away the mystery in the two slit experiment,and
other so called mysteries. To just say waves begs the questions "What
is a wave function"? What are the building blocks of waves? How does a
particle keep it wave moving with it;? Is space really the wave
created by the particle moving through it?" What is the length of the
shortest wave measured? How about the length of the longest radio wave.?
Do only radio waves go to infinity? Can waves be created or destroyed?
Do all types of waves end up as heat? etc. TreBert
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| User: "PD" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 02:48:54 PM |
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G=EMC^2 Glazier wrote:
Sam Best to think that all particles move in pairs staying parrel to
each other. That takes away the mystery in the two slit experiment,and
other so called mysteries. To just say waves begs the questions "What
is a wave function"? What are the building blocks of waves? How does a
particle keep it wave moving with it;? Is space really the wave
created by the particle moving through it?" What is the length of the
shortest wave measured? How about the length of the longest radio wave.?
Do only radio waves go to infinity? Can waves be created or destroyed?
Do all types of waves end up as heat? etc. TreBert
Only problem with this is that it also works with N-slit experiments,
where N > 2.
Now, you might then ask, does a particle move in N-plets, and how does
it know what N to choose before it gets to the slits?
PD
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| User: "RP" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 12:53:02 PM |
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GeordieSi wrote:
Very interesting. I'd pretty much come to the conclusion that it is
best to think of everything as waves. I can see the problems of trying
to explain clearly complex processes with very simple models but I've
been trying to imagine what properties such probability waves might
have. I seem to run into problems when I use a fixed speed of light in
the quantum model. I have a few naive (again) questions.
Reread Feynman's "QED: The Strange Theory of Light and Matter" for his
take on this.
Firstly I'd read some popular works on QED by Feynman. The sum over
histories approach seems to imply a variable speed of light (I'm
probably wrong about that).
Secondly, once when a wave is absorbed by an electron (which I guess is
also a wave) it must 'collapse' instantly otherwise I presume there
would be problems with the left over portion interacting with other
things.
Wheeler and Feynman grappled with this, but never produced a full
mathematical model of the resultant "Absorber Theory" that they
formulated. What is clear from that attempt is that Feynman didn't
regard photons as something distinct from the probability "wave".
The details involved in the collapse of the wave function resolve to
philosophical speculations, over which there have been many debates.
Some even came to conclude that consciousness was a physical contributor
to the collapse. These people were quite mad. Actually it was
Schrodinger's intent with his *simultaneously dead and alive cat*
thought experiment to show how ridiculous that speculation was. To this
day that argument has been misinterpreted as being something that he
believed and had concluded would actually occur.
As for the left over portion of the wave energy that my Bohm-like model
predicts, let me say again that there is no intrinsic energy in a wave.
It thus is possible for the quantum information contained in it to be
detected by separate observers. Sam Wormly just recently posted an
update stating that this had been confirmed, albeit I doubt that the
researchers involved know anything of my speculations, and thus couldn't
have known that they were inadvertently supporting my model.
However it would seem that this collapse would need to be
faster than the speed of light.
Of course. Which is why it doesn't happen.
Thanks again.
Richard Perry
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| User: "Henning Makholm" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 01:27:56 PM |
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Scripsit "GeordieSi" <simon@hopkins9666.fsbusiness.co.uk>
Firstly I'd read some popular works on QED by Feynman. The sum over
histories approach seems to imply a variable speed of light
How so?
Secondly, once when a wave is absorbed by an electron (which I guess is
also a wave) it must 'collapse' instantly otherwise I presume there
would be problems with the left over portion interacting with other
things.
Well, not necessarily. What really happens in QM is that there is a
single wave in a six-dimensional space where each point specifies a
position for the electron *and* (possibly) a position for the photon.
When the electron absorbs the photon, a bit of the wave seeps from the
"electron at such-and-such coordinates; photon at same coordinates"
point in the state space to the "electron at such-and-such
coordinates; no photon" point. The wave can have parts of its bulk in
the region of state space where there is a photon and other parts in
the region where there is none.
If there are more particles than a single electron and a photon, add
three dimensions to the state space for each. This quickly gets more
complicated than our native imagination can follow.
There is an often useful *approximation* in which each particle has
its own wave in ordinary 3D space. In some cases it provides workable
first-degree predictions, but it takes considerable finesse to guess
which those cases are, and it is known to _fail_ experimentally in
many other situations.
However it would seem that this collapse would need to be faster
than the speed of light.
It is true that the collapse of the wave must happen instantaneously.
Strangely enough, this does not cause any _observable_ conflict with
special relativity, which allows the two theories to coexist.
Nevertheless the "philosophical" mismatch between quantum collapse,
relativity, and causality continues to worry many theorists in their
idle hours (as well as innumerable hordes of crackpots who demand
that it should lead us to reject all accepted physics).
--
Henning Makholm "I, madam, am the Archchancellor!
And I happen to run this University!"
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| User: "GeordieSi" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 04:20:19 PM |
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I can see that the nature of probability waves divides opinion. It is
gratifying that at least my questions seem sensible even if my answers
are not. I'm still teaching myself the relavent mathematics so I have
to make do with crude visualisations at the moment.
I also realised I'd strayed into much trodden philosophical speculation
about how relativity and quantum theory fit together. I had read
somewhere that special relativity and quantum theory of light had been
welded together to form QED theory (and less happily in QCD). Am I
correct in thinking this? Is anyone brave enough to attempt a simple
explanation as to why general relativity does not coexist happily with
quantum theory?
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| User: "quantis" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 04:40:07 PM |
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GeordieSi wrote:
I can see that the nature of probability waves divides opinion. It is
gratifying that at least my questions seem sensible even if my answers
are not. I'm still teaching myself the relavent mathematics so I have
to make do with crude visualisations at the moment.
I also realised I'd strayed into much trodden philosophical speculation
about how relativity and quantum theory fit together. I had read
somewhere that special relativity and quantum theory of light had been
welded together to form QED theory (and less happily in QCD). Am I
correct in thinking this? Is anyone brave enough to attempt a simple
explanation as to why general relativity does not coexist happily with
quantum theory?
I was checking the archives to see what experts here commented
on RP model. Here's one by a veteran Old Man (who is now suffering
from eyesight problem and can't log in often):
RP said:
" Recall that, in the thread to which the OP refers, I posited that
the em waves pass through everything, never being absorbed, but
simply being superposed over destructively by secondary radiation
of the intercepted charges, i.e. that radiation produced by their
recoil."
Old Man answered:
"*****.
Optical Model: If there's a cross-section for absorption,
then the cross-section for elastic scattering is, at the least,
as large. That is, with absorption, elastic scattering occurs
in the complete absence of an elastic scattering potential.
[Old Man]
RP puts the cart before the horse. For the two slit
experiment, RP would place a potential for elastic
scattering whereof QM needs none. QM needs
naught but the potential for absorption to accurately
predict the elastic scattering (interference pattern and
diffraction envelope).
Rather than hypothetical, the parameters needed for
the absorption potential are phenomenological, and
not adjustable."
----------------------
Since Old Man is not here with us as he doesn't want
to waste his eyesight. Could someone explain in
details what Old Man mean above for us laymen?
Tnx.
Quantis
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| User: "RP" |
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| Title: Re: Double slit experiment confusion |
08 Mar 2006 07:06:48 PM |
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quantis wrote:
GeordieSi wrote:
I can see that the nature of probability waves divides opinion. It is
gratifying that at least my questions seem sensible even if my answers
are not. I'm still teaching myself the relavent mathematics so I have
to make do with crude visualisations at the moment.
I also realised I'd strayed into much trodden philosophical speculation
about how relativity and quantum theory fit together. I had read
somewhere that special relativity and quantum theory of light had been
welded together to form QED theory (and less happily in QCD). Am I
correct in thinking this? Is anyone brave enough to attempt a simple
explanation as to why general relativity does not coexist happily with
quantum theory?
I was checking the archives to see what experts here commented
on RP model. Here's one by a veteran Old Man (who is now suffering
from eyesight problem and can't log in often):
RP said:
" Recall that, in the thread to which the OP refers, I posited that
the em waves pass through everything, never being absorbed, but
simply being superposed over destructively by secondary radiation
of the intercepted charges, i.e. that radiation produced by their
recoil."
Old Man answered:
"*****.
Optical Model: If there's a cross-section for absorption,
then the cross-section for elastic scattering is, at the least,
as large. That is, with absorption, elastic scattering occurs
in the complete absence of an elastic scattering potential.
[Old Man]
RP puts the cart before the horse. For the two slit
experiment, RP would place a potential for elastic
scattering whereof QM needs none. QM needs
naught but the potential for absorption to accurately
predict the elastic scattering (interference pattern and
diffraction envelope).
Rather than hypothetical, the parameters needed for
the absorption potential are phenomenological, and
not adjustable."
----------------------
Since Old Man is not here with us as he doesn't want
to waste his eyesight. Could someone explain in
details what Old Man mean above for us laymen?
Old man glossed over the zpf contribution, and thus all of the finer
points involved. QED is a gross oversimplification of the events that
produces more open questions than it answers. Empirical consistency
notwithstanding. The TOE is still out there, and IMO the quantum venue
is the wrong venue. Statistics cannot be used to derive the
fundamentals from which they are themselves derived.
Every radio transmitter and receiver using multi-element antennae
operate precisely on the very principles of em wave superposition that
I've set forth as solutions to the single and double slit experiments,
as well as any other spooky phenomena reported. Old Man is typically
full of Old Hot Air. :)
http://www.citebase.org/cgi-bin/fulltext?format=application/pdf&identifier=oai:arXiv.org:quant-ph/9712001
http://irims.org/blog/index.php/questions/2004/09/25/questions_welcome
Richard Perry
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| User: "Ben Rudiak-Gould" |
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| Title: Re: Double slit experiment confusion |
19 Feb 2006 10:47:40 AM |
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GeordieSi wrote:
If I imagine placing the detector say to the left of centre behind the
'slits' then assuming that light has a finite speed then the photon wave
will take longer to reach the detector from the right slit than the left.
If they don't reach at the same time how can they interfere (assuming we
reduce the light intensity so that only one photon passes each time).
Hm, no one ever replied to this.
There won't be any interference in the situation you describe. Interference
happens when which-way information is lost; if the time of arrival at the
detector gives you information about which way the photon went, then the
which-way information wasn't lost. There will always be some uncertainty
about the time the photon was emitted and detected, and if this is large
enough then the arrival time might not tell you which way the photon went,
and in that case there will be interference.
-- Ben
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| User: "GeordieSi" |
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| Title: Re: Double slit experiment confusion |
20 Feb 2006 05:57:11 AM |
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Thanks for the reply. I realise if I try to get information as to the
path of the photon there would be no interference. I was trying to
think through the implications of the double-slit experiment. In
experiments at very low light intensity one can assume that only a
single photon passes through the slits. When these photons are detected
on say a photographic plate an interference pattern gradually builds up
(made up of individual strikes). This experiment would seem to imply
that each photon interferes with itself - or rather the probability
density wave passes through both slits to form the interference pattern
which dictates the distribution of the strikes on the photographic
plate. Although strange it seems logical. Or have I made mistake at
this stage?
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| User: "FAX" |
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| Title: Re: Double slit experiment confusion |
20 Feb 2006 09:55:56 AM |
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GeordieSi wrote:
Thanks for the reply. I realise if I try to get information as to the
path of the photon there would be no interference. I was trying to
think through the implications of the double-slit experiment. In
experiments at very low light intensity one can assume that only a
single photon passes through the slits. When these photons are detected
on say a photographic plate an interference pattern gradually builds up
(made up of individual strikes). This experiment would seem to imply
that each photon interferes with itself - or rather the probability
density wave passes through both slits to form the interference pattern
which dictates the distribution of the strikes on the photographic
plate. Although strange it seems logical. Or have I made mistake at
this stage?
What's a "probability denisty wave"? How fast does it move?
How do you measure it? What's is it made of? How big is it?
How do they "form" interference patterns?
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| User: "Peter" |
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| Title: Re: Double slit experiment confusion |
21 Feb 2006 08:56:36 AM |
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On Mon, 20 Feb 2006 03:57:11 -0800, GeordieSi wrote:
Thanks for the reply. I realise if I try to get information as to the
path of the photon there would be no interference.
The "Prowave Interpretation of Quantum Mechanics" is the simplest and
least confusing interpretation I have found so far.
http://www.quantummatter.com/wave.html
Roughly speaking, this interpretation assumes that:
1) Quanta of matter and energy always propagate as waves.
2) Interactions (transfers of energy) from one quantum to another
occur at a point and this involves a "collapse of the
wavefunction".
If assumption 1) is correct, then it is impossible in principle
to determine the path of a photon because photons always travel as
waves distributed in space.
Furthermore, according to 2) if a detector appears to detect which slit a
photon has passed through, then because the act of detection would involve
a transfer of energy, then the wave function of the photon would collapse
at that point, thus altering or destroying the original interference
pattern.
For me this removes some of the mystery as to why "getting this
information" destroys the interference.
Regards,
Peter
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| User: "Ben Rudiak-Gould" |
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| Title: Re: Double slit experiment confusion |
24 Feb 2006 12:53:27 PM |
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Peter wrote:
The "Prowave Interpretation of Quantum Mechanics" is the simplest and
least confusing interpretation I have found so far.
Roughly speaking, this interpretation assumes that:
1) Quanta of matter and energy always propagate as waves.
2) Interactions (transfers of energy) from one quantum to another
occur at a point and this involves a "collapse of the
wavefunction".
You get wrong answers if you collapse the wave function any time particles
interact. For example, you can do the double-slit experiment with atoms or
molecules. Their constituent parts are always interacting (else they'd fall
apart en route), but this doesn't lead to classical behavior.
Otherwise what you say above is fine, but I wouldn't call it an
interpretation so much as a description. Every quantum theory has a
Lagrangian that's local in spacetime, meaning that particles only interact
with other particles that are in the same place (at the same time).
Furthermore, according to 2) if a detector appears to detect which slit a
photon has passed through, then because the act of detection would involve
a transfer of energy, then the wave function of the photon would collapse
at that point, thus altering or destroying the original interference
pattern.
Well, I'd say it's a matter of the photon leaving some record of its
passage. Energy transfer is necessary but not sufficient for that.
-- Ben
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| User: "Peter" |
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| Title: Re: Double slit experiment confusion |
26 Feb 2006 06:02:07 AM |
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On Fri, 24 Feb 2006 18:53:27 +0000, Ben Rudiak-Gould wrote:
Peter wrote:
The "Prowave Interpretation of Quantum Mechanics" is the simplest and
least confusing interpretation I have found so far.
Roughly speaking, this interpretation assumes that:
1) Quanta of matter and energy always propagate as waves.
2) Interactions (transfers of energy) from one quantum to another
occur at a point and this involves a "collapse of the
wavefunction".
You get wrong answers if you collapse the wave function any time particles
interact. For example, you can do the double-slit experiment with atoms or
molecules. Their constituent parts are always interacting (else they'd fall
apart en route), but this doesn't lead to classical behavior.
Thanks for this correction.
I overlooked the distinction between "partial interactions" and "complete
interactions".
As explained at:
http://www.quantummatter.com/node4.html
"As the quanta propagate and interact with the macroworld, two separate
types of interactions occur. The first is defined as a partial
interaction: This interaction reorganizes or redirects the wavefunction
designated by a unitary transformation matrix. Examples of such are
beamsplitters and magnetic fields. The other type of interaction is
defined as a complete interaction: This is designated by the destruction
(and creation) of a quantum of energy, for example a bound electron
absorbing a photon."
Regards,
Peter
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