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Author Topic: Does the double-slit experiment work with all wavelengths of light?  (Read 10567 times)

Offline Ian Scott

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to all correspondents

It is simple to imagine a diffraction pattern from a wave emerging from two splits. What you fail to grasp is non measurement - as the act forces a particle behavior and the wave effect is lost.

Why is this hard for you?

Maybe quantum physics is too simple it needs child play

 

Offline Ian Scott

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this commentary remains absurd - from two silly slits in a piece of paper. The wave probability function "propagates" through both isn't that obvious? There is nothing hard to understand in this.
 

Offline Madidus_Scientia

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this commentary remains absurd - from two silly slits in a piece of paper. The wave probability function "propagates" through both isn't that obvious? There is nothing hard to understand in this.


I don't think you actually know what you're talking about. I certainly don't. To quote Richard Feynman "If you think you understand quantum mechanics, then you don't understand quantum mechanics."
 

lyner

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I never can understand the obsession with the Two Slits Experiment. Diffraction happens everywhere. All the arguments rehearsed here apply in every em interaction in the Universe. People seem to want photons to be different when in a very simplified context.
 

Offline lightarrow

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this commentary remains absurd - from two silly slits in a piece of paper. The wave probability function "propagates" through both isn't that obvious? There is nothing hard to understand in this.

You have written correctly: THE WAVE propagates through both slits, NOT THE PARTICLE:

Quote
so the photon must be going through both holes at once, if it is a particle

THE WAVE it's not THE PARTICLE. Can you understand the difference?

If you don't consider this important difference, you can forget talking of QM.
 

Offline JP

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I never can understand the obsession with the Two Slits Experiment. Diffraction happens everywhere. All the arguments rehearsed here apply in every em interaction in the Universe. People seem to want photons to be different when in a very simplified context.

I think it's a beautiful experiment because it was so useful in overturning previously held beliefs and contains an incredible amount of physics.  The problem is that people assume that the 2-slit experiment is just one experiment that always shows wave/particle duality.  All it really does is show that whatever forms the interference pattern behaves as a wave.  This has been a huge step at different points in the history of physics, however, and is still one of the most dramatic ways to demonstrate wave behavior.  (I'm biased here, since I do work in coherence theory, but its still a nice experiment!)

1) Classical light:  The 2-pinhole experiment verifies that light is indeed a wave since it shows interference patterns.  You can also investigate the coherence properties of light (i.e. how much randomness is involved--varying from very random/incoherent for black bodies to very ordered/coherent for lasers). 

2) Relativistic quantum mechanics:  You can explain what's going on by field theory/path integrals.  The particle takes all possible paths from each slit, but because of the mathematics involved in QM, only some of the paths end up being useful.  There's a great deal of similarity between this and the classical waves, because the mathematics of QM wavefunctions and the mathematics of classical waves end up being similar: i.e. waves can cancel each other out just like the probability wavefunctions.  This does show wave/particle duality if you use relativistic electrons, which we already knew behave as particles in many applications. 


But I agree with sophiecentaur.  The strength of the experiment is in demonstrating that whatever you're shooting at it is a wave.  Since most of us would have no doubt about the wave nature of photons (they make up light waves, after all), watching them behave as waves isn't really a surprise...  For photons, what is interesting is watching contexts (the photoelectric effect) there they behave as particles rather than waves.
 

Offline lightarrow

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The strength of the experiment is in demonstrating that whatever you're shooting at it is a wave.  Since most of us would have no doubt about the wave nature of photons (they make up light waves, after all), watching them behave as waves isn't really a surprise...  For photons, what is interesting is watching contexts (the photoelectric effect) there they behave as particles rather than waves.
More precisely, I would say that they behave as particles exactly when they are detected. What do you think?
 

Offline JP

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Generally, yes.  Usually your field is strong enough to think of it as classical waves, and you then have so many photons hitting your detector at once that you can't pick out each individual hit and just see intensity fringes.  If, however, you dial your field down so that you expect only one photon in the detector at a time, then you'll probably see individual "clicks" of detection.  You can go back and forth between the models, relating intensity to photon hits, but it generally requires some sophisticated mathematics because you're dealing with quantum statistics.
 

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