Problem with the two slit experiment, Observing later

Hi Laserlight,

Re:Your detailed explanation..

We differ in that I see the DSE as an instrument that analyses 'reality'. We have an exemplary experiment here http://www.teachspin.com/instruments/two_s...periments.shtml and an exemplary result here http://www.teachspin.com/instruments/two_s..._combiplot2.gif . We can use 'other knowledge' to establish that the slits do not need to be very accurately cut and do not need to be made of any specific material.

Among many other things the DSE is in apparatus that enables us to measure the wavelength of light as long as we know the distance between the slits and the distance to the screen. It is generally accepted that the single slit before the pair of slits is an important part of the apparatus as it seems to be required to ensure both slits receive the same information and that is 'in phase'. ( see ripple tank http://www.echalk.co.uk/Science/Physics/ri...Tank/ripple.htm ).


You don't make any attempt to show that your assumptions can predict the observed result. With all due respect I think it is evident that a device operating in the way you describe could not be used to measure the wavelength of light therefore you are not describing the DSE that we know and love. It is certainly interesting to consider the type of second order effect that you have described. With a proper explanation of the DSE we could try to answer the question "Why do these effects have so little influence on the observed result?" but at present we lack that proper explanation.

I assume 'seeking all paths' originally came (probably) from Feynman, subsequently used by Good Elf. I think it would be fair to say that both intend 'seeking all paths' to mean exactly that. There is nothing special about the path between the slits .. it has no greater or lesser probability than any other path .. in particular it has no greater probability than a path that heads directly for the screen. 'Seeking all paths' is one of the reasons why your proposed explanation fails.

Are you claiming the distribution of these 'patterns' follows the same pattern as that observed in the DSE? You have given no reason why that might be so.
I see no problem with Visser's papers as analyses of experiments conducted using gold materials and very narrow slits which are separated by just a few wavelengths of light.
Best wishes,
-C2.
Here is yet another DSE applet which predicts the observed result.
http://galileoandeinstein.physics.virginia.../youngexpt4.htm

Hi all,


Well C2, if given the choice between your preferred "classical" explanation, and the current "quantum" explanation, I too would choose the classical. The lesser of 2 evils, as it were.

I just wanted to comment right now, on your statement:

Most of the papers, authored by Visser (et al), that were presented, were NOT concerning slits of a few wavelengths, they were sub-wavelengths; an important distinction.


regards,

T.Roc

ps: on this last link to another DSE, click "show path difference", and notice the "evolving triangles" that I have tried to explain with words (not too well)

Hi TRoc,

[quote=TRoc]Well C2, if given the choice between your preferred "classical" explanation, and the current "quantum" explanation, I too would choose the classical. The lesser of 2 evils, as it were.[/TRoc]

I am hoping that one day we might see the classical solution as being no more and no less than the superposition of many 'quantum' solutions, for this to happen (obviously) we must get the right quantum solution. If we had both solutions then we would have an immensely powerful tool for exploring the relationship between the 'classical' and the 'quantum' world.

One day maybe someone will post "Hey .. I can see where the E field comes from!", or maybe not.

And I suspect that is just of the tip of the iceberg of what is to be seen in the DSE.

Best wishes,

-C2.

Hi C2,

I think that you are looking at things too simplistically, and incorrectly.
The results at the screen are the second order effect....they are the result
of events taking place at the slits, which is the first order mixing
event.

IMO, the wavelength of light can be fairly easily derived as was done by Young.
I do not need to prove the wavelength of light to understand the mechanism
of why waves of light interfere. They will interfere regardless of the wavelengths
used in the DSE, and present different interference bands as a consequence of
the frequency used.

Probability has nothing to do with interference or the bands, they will always
present the same pattern if the same wavelength and same slit geometry is
used. Trying to explain the physical mechanism that creates a consistent result
by using math is like trying to explain how a car goes from point A to point B
by using Pi to count the revolutions of the wheels. It doesn't explain the
actual physics, the underlying mechanisms, it only provides the formulas that yield
a result.

Visser's paper(s) were designed and constructed to find out the mechanisms using
some exotic methods to highlight the underlying phenomena at work in the
DSE. Did you read them? The idea is that if you can understand how and why
a phenomenon responds under idealized and designed conditions then you have
a fundamental baseline model from which you can make predictions and control
the experiment. That is what experiments are....controlled, designed tests that
are used to gather useful information from which the observed results allow one to
make and apply predictions to similar conditions that cannot be easily observed.
Visser's paper showed exactly how the peak intensity interference patterns
between the slits correspond to the banding results imaged on the screen. Same
number of interference intensity patterns at both locations.... Coincidence? I don't
think so.

You keep throwing up math as the answer. Math isn't a physical phenomenon,
it is merely number patterns that yield number results. Math is used to verify
predictable results, it has nothing to do with the physical mechanisms that
generate the predictable results. Contrary to your beliefs, the cancellation of
overlapping wavelengths is NOT HAPPENING AT THE SCREEN. The interference
is happening at/between the slits which is the point of constructive and destructive
interference signal mixing.

Are you expecting us to believe that 700nm wavelengths of light are perfectly
cancelling across an area of 1-2 millimeters and don't change their phasing relationship when the screen is moved back and forth, regardless of the position
of the screen? Why do you think the apex of the triangles that are used to
generate the mathematical results have their focal point at the slits? It is the
focal point of projection, the same as you would get with a movie projector,
nothing more.


Regards,
LL

Hi TRoc,

It's always easier taking the traveled path because you know what to expect,
but familiarity breeds complacency and offers no challenge.

Anyone can drive a car by turning the key and pushing the pedal, and for
some that is enough. For true seekers, it isn't. It depends on your comfort zone.

To coin an old phrase....."Ignorance is bliss".....LOL!

Regards,
LL

Hi all,


LL,
Don't take what I just said for: I (or we should) give up, the classical explanation is the final answer, or your version = the quantum version. To that, I mean the "probabilistic" method.

I do have reservations as to the plasma (plasmon) at the slit idea. I am not an expert in Polaritonics, but I know that there are several versions that have been proposed. One difference is the direction of propagation in the lattice; I believe the Surface Plasmons run perpendicular to the surface. That would make "coupling" hard, but shouldn't be enough to kill the idea. Also, keep in mind that the phonon speed will not be fast enough to couple with an EM wavefront, which is where the effect would seem to be required.

The slit wall thickness to slit width ratio does play a role, not commonly mentioned.

versus

http://www.optics.rochester.edu:8080/users.../diffthick.html

More information on the diffraction of terahertz radiation by an aperture can be found in the papers:

Spatiotemporal shaping of terahertz pulses
http://www.optics.rochester.edu:8080/users.../bromage971.pdf
Jake Bromage, Stojan Radic, G. P. Agrawal, C. R. Stroud, Jr.,
P. M. Fauchet, and Roman Sobolewski
Opt. Lett. 22, 627 (1997).

Spatiotemporal shaping of half-cycle terahertz pulses by diffraction through conductive apertures of finite thickness
http://www.optics.rochester.edu:8080/users.../bromage981.pdf
Jake Bromage, Stojan Radic, G. P. Agrawal, C. R. Stroud, Jr.,
P. M. Fauchet, and Roman Sobolewski.
JOSA B 15, 1953 (1998).


For the general debate, I will add this as well:

In the most basic, and general sense, we have these 2 thoughts. 1.) without the slit(s), we get no pattern at the screen. 2.) without the screen, we get no pattern from the slits. What I mean here (again), is the measurement problem. We can not "prove" either because it takes both, with certain distances/properties, to get the desired result. This is why I say that energy is a "verb", or 2 party interaction. What we are talking about, is the appearance of the pattern on the screen, which may, or may not match the energy levels there. Here, I'll remind C2, that I am not talking about "intensity" only (#'s of "photons"); we have a "dark energy" as well. (aka negative frequencies, negative energy, retarded solutions, whatever dualistic symmetrical properties/anti-properties that have been put forth).


ciao,

T.Roc



This post has been edited by TRoc on Feb 25 2007, 09:42 PM

This post has been edited by TRoc on Feb 25 2007, 09:45 PM

(disregard the board error above)



Hi all,


From that last paper, "Spatiotemporal shaping of half-cycle terahertz pulses by diffraction through conductive apertures of finite thickness"
http://www.optics.rochester.edu:8080/users.../bromage981.pdf

(emphasis added)

Add that to my point that we are propagating light in this experiment through a mixed "random" medium of air.

Now, take "Anderson localization", which has made a "shift" (localization-delocalization transition), and our "random" medium becomes "not so random" anymore. In fact, it becomes comparable to bandgaps in other materials.

http://en.wikipedia.org/wiki/Anderson_localization

(emphasis added)

GE has pointed out this "fixed mode" in our cavity, but you can see that he is "right, but for the wrong reasons". (just like Mr Huygens; not bad for an elf!) The modes are fixed, but they certainly will change, from the equilibrium state prior to turning on the laser (or opening the slit to a light source), and the commencement of the experiment.

More, from "The Encyclopedia of Nonlinear Science" (Routledge 04) - Anderson localization

If we take both solutions of the EM wave, like a Cramer transaction, we have a connection between both ends. Ge has also alluded to the modes, and conductivity in air for such electrical phenomena as ball lightning. At any rate, we are certainly providing "thermal activation" in the DSE, so we can expect some changes in the conductivity of the medium. (refractions, absorptions/transmissions, etc.)

A little "semantic filtering", and we have different energies = dissonant; similar energies = resonant. This means the resonant energies are spatially separated, like our bright bands, while beat-frequencies contribute to the darkness between the energies. "Photons" are hitting the screen everywhere, but Resonance gives us the pattern we see.

These last 2 quotes seem to suggest that the distance between the slit and the screen is all that is needed to cause the scaling of the pattern, due to the amount of overlaps created in the "triangle pattern" of the spread. It is also critical to realize that we can change materials in EITHER the slits OR the screen, and still get our diffraction pattern. The only constant (regarding mass, or electrons) is the air that exists "in between". This is also (IMO) the ONLY explanation for the "1-at-a-time" RANDOM build up of the diffraction pattern. The only real thing changing in that set-up, is the "thermal activation levels" are lowered as far as possible. The same process takes place however, because the "probability" for a quanta of energy to hit/interact with the SAME electron in the post-slit medium >>0. This means the pattern is STILL going to appear, albeit "chisled out of randomness", one bit, by one bit.

In this model, they use the term "mobility edges" to describe the "area" between the extended, and localized states of a wave packet. In my terms, this is the beat-frequency, which can only "wholly" reconstruct itself through specific ratio combinations, as is logically called for.



regards,

T.Roc



This post has been edited by TRoc on Feb 25 2007, 11:12 PM

Hi TRoc,

I appreciated the graphics....now imagine what would happen in the top version
if you had 2 closely spaced slits as the expanding wavefronts mix between them.

If you look closely at the graphic as the wave expands along the rear wall as it
departs the cavity of the slit, you will notice that it is nearly perpendicular to
the surface of the wall. If, as you suggest, dipolar plasmons are also perpendicular
to the wall, then the wavefront will cut across the dipole field at right angles and
the fields will interact....do you agree, or no? To carry this further, if you now
consider 2 fields approaching from 2 spatially separated slits they will mix
according to their mutual phase relationship at various points as they cut cross the
dipole field(s) oriented at 90 degrees to their "lateral" expansion. IMO, these are
"fixed" atomic standing waves that represent interference mixing points between the
slits.

I am not so sure how to interpret Visser' plasmon travelling between the slits because it seems logical that if plasmons were travelling they would move toward
each other from each slit and meet in the middle between the slits where they
would superpose and double the energy at that point.....this does however, offer
a possible explanation of why the high intensity point observed on the screen is
always centered between the slits, but that could also just be the maximum
superposition point where the two laterally expanding wavefronts are "overlapping"
at the centerpoint between the slits.

I am proposing that the number of EM field dipoles that are manifest between the
slits arrange their locations by charge equalization according to the dimension of
the center wall. The number of equally spaced plasmons determines the number
of harmonic signal mixing points along the slit wall. The wider the wall between
the slits, the more plasmons that are equally spaced along it, which yields more
mixing points and interference bands that are detected at the screen. The
narrower the slit gap the fewer plasmons and the fewer interference bands
projected onto the screen.

These plasmon dipole locations are the signal cancellation points between the
expanding lateral wave fronts and represent the nodes of the standing waves
that are projected onto the screen. The slit output wall and the number of
plasmons spaced on it establishes standing waves between the two wavefronts.

The areas between the plasmons are superposition points of signal mixing, where
the intensity/energy of the two wavefronts constructively add. These become the
maximum energy radiation superposition points of the interfered wavefronts.

http://id.mind.net/~zona/mstm/physics/wave...erference1.html

http://www.colorado.edu/physics/2000/schro.../two-slit2.html

note: Change the superpositon phasing with the pulldown by clicking in the
waveform box. There are several types of waveform/phase mixing possible.

Other comments, analysis, discussion welcomed.
LL

TRoc,

Ok...now the coup de grace for air having a major effect on the dispersion pattern
of the DSE.
We still get the same pattern under vacuum conditions, where air has been
eliminated as a "variable". This is also true for observed electron interference
patterns. TOUCHE !

OUCH!

Comments?
LL

This post has been edited by Laserlight on Feb 25 2007, 11:24 PM

Hi all,


LL, I thought that we had already covered this?

Let me re-state (with reference): http://en.wikipedia.org/wiki/Vacuum

This time, I'll go all the way for you, including the "changes in the electrons" that I had mentioned before, that you didn't seem to catch.

There's your "huckleberry": we have to "prime" a vacuum pump with ...

GASES CONTAINING ELECTRONS !

Or the DSE !

So, again, if you can FIND an experiment with "photons" done in a DSE, please, DO TELL. I've looked extensively, and couldn't find anything. I did find one paper, that theoretically says the DSE WILL NOT work under vacuum, for much the same reasons as I've given. It is rather "poor quality" though (including translation), so I didn't include it. Here it is, if you're interested: http://arxiv.org/PS_cache/physics/pdf/0212/0212103.pdf

This was PRECISELY why I said earlier, that this is WHY you don't find "photon" diffraction in vacuum, and you MUST find electron diffraction in vacuum. The interferences of these waves are opposite/complementary.


ciao,

T.Roc

PS. Perhaps we can think of lightning as a "staggered, muti-slit" diffraction of light, caused by the random orientations of electron bearing molecules in the atmosphere. Remember, we do not see lightning in space.

This post has been edited by TRoc on Feb 26 2007, 12:31 AM

Hi TRoc,

LOL!....You are deep into one of my technololgy specialties now....
ultra high vaccum. I worked with high vacuum turbomolecular pumps and
cryogenic pumps for many years. Semiconductor processing and plasma
processes are done in this ultra-high vac environment. I am very experienced
working at vacuum ranges of 1 x 10^-9 (and ^-10)Torr. This was our baseline
pumping level with leak rates that were exceptionally low. With the right materials
and procedures in place, outgassing is a non issue. The mean free path of
gaseous molecules/collisions in this environment is on the order of miles....
FWIW, our cryo pumps operated at a temperature <9 K, and the pumping
efficiency was many thousands of liters/sec. Cryo pumps are basically freeze
traps for gas molecules. This is the realm of Bose Einstein Condensates at the
helium cold head collection array.

FWIW, I did plasma processing and worked with high tech RF plasma equipment
for many, many years. So I have a bit of insight into plasmas, vacuums, etc.
I don't have experience working in experimental laser technology, but have
used laser and spectral interferometer equipment for process endpoint detection.

The point being that the vast atomic spacing at these vacuum levels have
virtually no effect on photons or electrons travelling between them.

I looked for an experiment that I read sometime last year where the DSE was
done under vacuum conditions but could not relocate it. I'm sure it wasn't done
at the vacuum levels discussed above, but I would suspect that the electron,
neutron, and large particle DSE experiments were carried out near this low
vacuum level to minimize atmospheric contamination on the results.

http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality

Regards,
LL

This post has been edited by Laserlight on Feb 26 2007, 01:18 AM

TRoc,

If I'm not mistaken particle beam weapons travel thru vacuum very well, no
atmosphere required.

Regards,
LL

Hi all,


Well, LL, I understand what you're saying, but the simple, and sad fact is this DSE SHOULD be done, but apparently hasn't. You CAN NOT keep "virtual particles" from popping up. These things MIMIC what was there, as the "ghosting" articles that GE has posted, state.

I said NOTHING of "propagation" in the "lightning" analogy. And NOTHING of "particle beams" in space. I know a laser will propagate in space, but will it diffract, and produce the "classic" pattern? The thin film (diffraction) experiments that I have seen, done in space by NASA, CONTRADICT current theory, point blank!

Certainly, with all of the equipment that you mentioned being necessary, we no longer have the "classic DSE", do we? The first post, that I mentioned Anderson localization in, specifically stated "even in zero temperature", so you have NOT alleviated my concerns here. What material(s) are you going to use in order to prevent the blocking of the slit? (by condensation) What about the key factor of conductivity?

Find that paper, and post it; otherwise, consider your "touche" parried.


regards,

T.Roc

Hi all,


Just a couple things that I would like to add to my last post.


Just about every other day, somebody posts a NEW and different source of DSE analogy. There is an ABUNDANCE of information available on the net, and elsewhere. Many, many experiments done in recent years are just creative variations on the theme. Why is it SO hard to find ONE experiment, with the DSE "photon" done in vacuum? This bothers me.


One thing that we have gone over many times, is "path length". I offered the "historical", lessor known "cornu spiral" (Fresnel Integrals) a few times.

http://mathworld.wolfram.com/CornuSpiral.html

A Cornu spiral describes diffraction from the edge of a half-plane.



A plot in the complex plane of the points

where S(t) and C(t) are the Fresnel integrals (von Seggern 1993, p. 210; Gray 1997, p. 65).




I find it hard to physically interpret the mean free path being "miles long", within the cavity of the DSE, although, I understand the MATH that says this should be. LL has recently questioned the abstract use of MATH to gain clear explanation of any particular phenomenon. If we are NOT removing ALL of the electrons (and positrons), then physically, they can't be "miles" apart, and still be in the "box". If they are "standing waves", then we have an infinite amount of harmonics that are symmetrically spaced from the center "point" to the end of the "miles long" path. As far as interference is concerned, these harmonic wavelets are still filling the space of the post-slit cavity. This is in agreement with the zero point fluctuations that was mentioned in the last post, as well as the indeterminacy of position of the electrons that appears in measurements.


regards,

T.Roc