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Double Slit Experiment

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Stookie

I thought this was a pretty cool video. I'm familiar with the subject, but love the way it's demonstrated here. I wish I had this guy as my physics teacher - I would have paid more attention.

http://www.wimp.com/doubleslit/

CFTraveler

Very cool.  Consider it stolen.

Stookie


Xanth

That's nuts!!

O_o

Consider my mind BLOWN!!  LoL

Timandra

I love this! First saw it on "What tHe bleep Do we (k)now!?"  8-)
Some things have to be believed to be seen ~ Ralph Hodgson

vladjackguy

It's because we can't determine the position of a moving electron when it's moving on an orbital.
WHEN THE POWER OF LOVE WILL OVERCOME THE LOVE OF POWER THE WORLD WILL KNOW PEACE~Jimi Hendrix
In the darkest place the littlest light is the brightest.~vladjackguy

Yamabushi

#6
I think David Bohm had it right with his pilot wave mechanics. Consider: the smallness of the scintillations on the screen suggests we are still dealing with a particle, not a continuous wave. The diffraction and interference patterns suggests that the motion of the particle acts like or is directed by a wave. In Bohmian mechanics a system of particles is described in part by its Schroedinger wave function - but the wave function provides only a partial description of the system. It is completed by the specification of the actual positions of the particles - this evolves according to the "guiding equation," which expresses the velocities of the particles in terms of the wave function. In other words, the configuration of a system of particles as it moves through space/time evolves via a deterministic motion choreographed by the pilot wave function. In particular, when a particle is sent into a two-slit apparatus, the slit through which it passes and where it arrives on the photographic plate are completely determined by its initial position and wave function.

Much like Bell, I don't see why this idea is generally so well ignored despite its natural and simple reconciliation of the wave-particle dilemma. Then again, physicists don't like the idea of a hidden variables domain. Granted, this does not clarify the nature of the relationship between the act of observation / measurement and the pilot wave (i.e. why is it less wave-like in the presence of an observing or measuring vector?).

CFTraveler

Perhaps because detection of any kind implies some sort of contact, collapsing the function?  (You can see by my answer that I don't completely grasp the problem- but humor me)- the question I have is, if it is always a particle whose location can be described by a wave function (which is how I understand what you just said, lol), why does it interfere with itself?  Isn't this a result of multilocation in one given moment?


Yamabushi

#8
Quote from: CFTraveler on February 17, 2010, 21:45:03
Perhaps because detection of any kind implies some sort of contact, collapsing the function?  (You can see by my answer that I don't completely grasp the problem- but humor me)- the question I have is, if it is always a particle whose location can be described by a wave function (which is how I understand what you just said, lol), why does it interfere with itself?  Isn't this a result of multilocation in one given moment?



Had a feeling you'd be the next reply.

Yes, you're right... it should be recognized that this (absence of the interference pattern in the presence of measurement) must involve interaction with another system that must also be included in the Bohmian mechanical analysis. The key element here is the notion of the conditional wave function of a subsystem of a larger system. In other words, since observation/measurement implies interaction, a system under measurement cannot be a closed system, but rather a subsystem of a larger system that is closed (the entire uni/multiverse?). So yeah, the configuration of the subsystem (electron or particle) also depends upon the configuration of the environment it exists in.

To your latter question: the motion of the electron is a product of the state of the pilot wave that determines it. Like any wave, a pilot wave can interfere with itself via diffraction. When the electron passes through the apparatus, and nothing is there to see which slit it goes through, the pilot wave diffracts and this change is reflected in the electron's motion trajectory.

It still doesn't really answer my question, though. To illustrate what I mean, I'll pose another question: why does measurement cause the collapse of the wavefunction, instead of the other way around? Is there any reason it should or shouldn't do one or the other (there appears to be), and if so, then what is that reason?
YB

Stookie

Can you make a video with a flying robot head to explain that please?

CFTraveler

Quote from: Stookie on February 18, 2010, 11:16:13
Can you make a video with a flying robot head to explain that please?
I second that emotion.   :lol:

CFTraveler

Quote from: Yamabushi on February 17, 2010, 22:51:32
Had a feeling you'd be the next reply.
Hee hee.  My little brain is still trying to comprehend in terms of 'pilot wave' or probability wave, and superposition is the only thing that it seems to understand.  It's that dang 'counterintuitiveness'.

QuoteIt still doesn't really answer my question, though. To illustrate what I mean, I'll pose another question: why does measurement cause the collapse of the wavefunction, instead of the other way around?
I have the suspicion that it has to do with the system not really being closed, although my brain hasn't caught up with my thinking.


QuoteIs there any reason it should or shouldn't do one or the other (there appears to be), and if so, then what is that reason?
YB
I can't wait for your answer.

pondini

#12
maybe they should bring the back panel closer to the double-slit panel -just close enough to allow the particles to collide -if that's truly what they're doing- but far enough away to determine their position afterwords. yes, i know i've wasted my time and yours by assuming brilliant minds would have overlooked this, and besides, i have no idea if the wave-lengths or frequencies are conducive to my hair-brain idea:P

is there an explanation (in lay-speak) that demystifies the conversion of the initially fired single particle into two? (if indeed that's what happens.) and does that conversion happen in the presence of an observer, and if so, why wouldn't it happen in the chamber of the gun?

i'm really no where near being qualified to ask these questions, so if you feel inclined, just shoo me away:)

ah, before i forget, i just wanted to say that if all i understand about QM/QP/QT is correct, then it seems we can not have a unified theory without including consciousness! what i find interesting is how The Buddha had understood this stuff 2300-2550 years ago (and even earlier in Hinduism). if i understand the early concept of 'Rta' correctly, it basically describes what the double-slit test displays -the automatic built-in self-regulating mechanism that governs the cosmos. lol, that's a cool definition!

thanks:)

CFTraveler

Pondini wrote:
Quotei'm really no where near being qualified to ask these questions, so if you feel inclined, just shoo me away:)
I think they're really good questions, and I think I read the answer to the first one (about the wavelength size vs. the slit separation), but IIRC it has to do with the angle of the pilot wave vs. the width of the slit.
I wish Yamabushi would come back and answer.
Anyway, I know I'm not qualified to answer them.

Yay for the non-qualifiers!
:lol:

pondini

Quote from: CFTravelerIIRC it has to do with the angle of the pilot wave vs. the width of the slit.

i think i understand. a very slight angle of trajectory would cause the wave to hit the panel every time and stop if the wave is too compressed...? a random pilot trajectory wouldn't help matters, either.

i say shoot them through cube of jello, lol j/k.

moondial

Quote from: Yamabushi on February 17, 2010, 21:20:31
I think David Bohm had it right with his pilot wave mechanics. Consider: the smallness of the scintillations on the screen suggests we are still dealing with a particle, not a continuous wave. The diffraction and interference patterns suggests that the motion of the particle acts like or is directed by a wave. In Bohmian mechanics a system of particles is described in part by its Schroedinger wave function - but the wave function provides only a partial description of the system. It is completed by the specification of the actual positions of the particles - this evolves according to the "guiding equation," which expresses the velocities of the particles in terms of the wave function. In other words, the configuration of a system of particles as it moves through space/time evolves via a deterministic motion choreographed by the pilot wave function. In particular, when a particle is sent into a two-slit apparatus, the slit through which it passes and where it arrives on the photographic plate are completely determined by its initial position and wave function.

Much like Bell, I don't see why this idea is generally so well ignored despite its natural and simple reconciliation of the wave-particle dilemma. Then again, physicists don't like the idea of a hidden variables domain. Granted, this does not clarify the nature of the relationship between the act of observation / measurement and the pilot wave (i.e. why is it less wave-like in the presence of an observing or measuring vector?).

BANG!!!!

That was my head exploding! :-D

I have no idea what you just said but I reckon it was very clever!! ;)

Cheers

Kev
http://www.webmasterwebsitedesign.com

Search Engine Friendly Website Design

Pauli2

It's not the two slit experiment that is strange. It's the one slit experiment.

You get full interference pattern even with one slit if it is of the appropriate width. Even with electrons.
Former PauliEffect (got lost on server crash), http://en.wikipedia.org/wiki/Pauli_effect

teckner

Quote from: CFTraveler on February 17, 2010, 21:45:03
Perhaps because detection of any kind implies some sort of contact, collapsing the function?  (You can see by my answer that I don't completely grasp the problem- but humor me)- the question I have is, if it is always a particle whose location can be described by a wave function (which is how I understand what you just said, lol), why does it interfere with itself?  Isn't this a result of multilocation in one given moment?



Yep. When you see your legs, they don't move because photons which bounce off of your legs and into your eyes are not nearly heavy enough to move your legs in a conceivable manner. However, electrons and photons have close enough size/mass that when a photon were to touch an electron, the function will collapse.

tenshi_R

i just remembered that when testing electric circuits  the test equiplemt still puts a minimal load on the system( depending on the  test equipment) a simple light bulb connected to a wire would draw power from the system, a voltmeter would draw less power to move the coil, a digital voltmeter would draw even less power but still does.

a microphone still absorbs sound waves and converts them.
light sensing diode im assuming also absorbs waves when exposed to them( im not sure how they work exactly)

how does your eye work? does your eye also absorb light waves and transform them into signals to your brain?

if so then any test equipment would be altering the ballance of the system, and maybe its enough to have an effect on particle.

Pauli2

Quote from: tenshi_R on November 06, 2010, 03:13:19how does your eye work? does your eye also absorb light waves and transform them into signals to your brain?

if so then any test equipment would be altering the ballance of the system, and maybe its enough to have an effect on particle.

The human eye can detect as little as 5 (five) photons at a time. The photons are not light waves, but particles with wave characteristics. Yes, every measurement affects the object.

http://en.wikipedia.org/wiki/Uncertainty_principle explains the limit: h/(4*pi)
Former PauliEffect (got lost on server crash), http://en.wikipedia.org/wiki/Pauli_effect

Capt. Picard

#20
Never mind, reread it I get what you're saying now.