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Wave-particle duality

  1. Feb 24, 2007 #1
    I've been racking my brain to no end trying to feed my crack physics fix. I've even managed to abandon sleep and school work to indulge in this addiction. :tongue:
    Anyways Am I looking at this right? I just want some sort of guidance so I'm going in the right direction with this.......
    When a particle-wave is interfered with and behaviorally becomes a particle (collapsed wave function) - it seizes to interfere with itself thus not exhibiting wave properties. So the act of measuring causes a photon/ electron to still retains all of its properties it just looses its ability to interfere with it self,which means it passes through only one hole.... and here I'm sort of iffy on a couple of things...
    I understand the uncertainty principle, but I do no see how that explains the particle-waves behavioral change in going threw one slit or the other.
    ... is it just probabilistic at that point slit 1 or slit 2? I also assume that a collapsed wave function is irreversible?
    ...from my understanding the photon/electron still makes its way to the screen except no diffraction and interference patterns... so how/why does it travel exactly? from the momentum carried from its particle-wave "trip"? or is this something unmeasurable due to HUP? Also is there room for HUP and for the conscious observer to co-exist in explaining particle-wave duality?
    (something interesting to read on the topic)
    Thanks for the help...if possible could I get comments or answers not so heavy on the math, or more preferably along side it so I can "follow along":blushing:
  2. jcsd
  3. Feb 24, 2007 #2
    The superposition is the key to understanding why the particle appears to travel through both slits and then interfere with itself. Once you grasp what a superposition is in terms of being a series of possibilities for the photons wave like motion, then you can grasp what happens in decoherence, here is a good place to start though.

    Feynman's two slit experiment

    I love this website, it's very simple and clear and involves no maths whatsoever, so even the maths knowlessman can pick it up, although to really understand the intricacies of it you will need maths.

    To put it simply before the wave decoheres it's superposition travels through both slits, it's "waves" then interfering with itself (like a water wave would) And producing an interference pattern. If you decohere the superposition then it's superposition dissapears, and it no longer behaves like a wave, striking the back of the screen as if it were a particle.

    With a detector at both slits, so that the photon is always decohered, the statistical probability of the photon going through one slit or another is 50/50.
    Last edited: Feb 24, 2007
  4. Feb 24, 2007 #3
    Thanks. I will read that.
  5. Feb 25, 2007 #4
    I just wanted to briefly comment on this. It's true that when an object is observed, its wave function collapses to a single point. You can imagine this as a continuous graph on an xy plane collapsing to a spike of infinite height at some point on the x-axis (in mathematical terms, this is called a Dirac Delta Function). However, it's important to note that this is not a permanent situation. After being measured, an object's wave function will slowly spread out again until it is measured again. So it is not as though the act of measurement robs any particle of its wavelike properties.
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