About light and its dual nature.

Discussion in 'Physics & Math' started by cato, Aug 31, 2005.

  1. cato less hate, more science Registered Senior Member

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    I recently had a fever, and while lying in bed burning up, I decided to take my mind off it by thinking about physics, when I had an interesting thought.

    most people say light behaves like a wave and a particle, but I don't think thats true. we never actually observe light as a particle, during or at the end of its trip, the only thing that happens is that an electron (or several) absorb the whole energy of the wave in a finite point, which fools us into thinking of the light as a particle, when in fact we are just looking at the particle-like behavior of the electron.

    so basically, we don't have a duality at all, we just have a quantized wave, which we are tricked into thinking of it like a particle by the particles it interacts with.

    just a crazy, fever induced, idea I had. any thoughts?
     
    Last edited: Aug 31, 2005
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  3. Aer Registered Senior Member

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    I imagine some people like to think of photons as particles, such as James R with his bosons example in another thread.

    However, the duality is for electrons. Electrons behave both like a particle and wave. See the double slit experiment.
     
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  5. cato less hate, more science Registered Senior Member

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    are you trying to correct me? "photons" were, I think the first thing to be attributed a dual nature. electrons, protons, even molecules have been shown to have a dual nature. not just electrons bro, a Vienna team has gotten the effect all the way up to tetraphenylporphyrin, about 2nm in diameter. light was/is one of, but not the only, things they attribute this duality to.
     
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  7. Aer Registered Senior Member

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    Do they also peer into their ass?

    OK - instead of refering to authority, let's just analyze the situation here:

    We already know that light behaves like a wave, this is well established.
    Some people claim "photons" have a particle nature. In what ways do photons physically behave like particles?
     
  8. Aer Registered Senior Member

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    Here we go:
    Particles
    * have mass (inertia)
    * respond to forces (acceleration)
    * have momentum (mass x velocity)

    Photons are said to have momentum, p=hf/c as described by QM.

    But like I said, this still doesn't make a photon anymore like a particle to me because photons do not have mass and do not respond to forces. Perhaps the classification that only particles can have momentum is erroneous.

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  9. cato less hate, more science Registered Senior Member

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    yeah, I tried to avoid calling it a particle for those reasons, but I did accidentally say it at the end of my post. otherwise, we are in agreement. I also have a spelling error there, I will fix them both now.
     
  10. Pete It's not rocket surgery Moderator

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    If one of the defining features of a particle is that it has mass, then photons are not like particles.

    Of course, one might question whether Aer's list of defining features is a well-accepted one, or whether he peered into his ass and found it there.

    Radiation pressure can be measured directly. See Nichols Radiometer. The pressure measured agrees with that predicted for the momentum of photons.

    The photoelectric effect shows that light waves are absorbed by electrons in discrete packets, with energy set by the frequency of the light. I fail to see how this happen if light is simply waves, but I'm willing to be enlightened.
     
    Last edited: Sep 1, 2005
  11. Pete It's not rocket surgery Moderator

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    A quick Google turned up several kinds of devices that detect inidividual photons, and alos devices that produce individual photons.
     
  12. UnderWhelmed Registered Senior Member

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    Does this make any sense?

    All matter can be broken down into energy waves. The waves lengths are in fact so small that they appear to act as single particles. Perhaps particles are just illusions, created by flawed observations a few hundred years ago.

    Here's a cool java of the double slit experiment: http://www.falstad.com/ripple/ex-2slit.html
     
  13. UnderWhelmed Registered Senior Member

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    What about if the photonic waves interacted with the electron waves and caused a type of resonance where the energy of the wave increased and caused the electron to escape...or something like that.

    Again I have no proof, just throwing it out there.
     
  14. Aer Registered Senior Member

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    Very good point. To be honest, it was the first list I found. I should have warned that I am not sure if those attributes are generally accepted.

    I think the first thing you must do is define precisely what a wave is on the quantum level. I am not so sure it is the same thing as an ocean wave..
     
    Last edited: Sep 2, 2005
  15. Aer Registered Senior Member

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    Photons as discreet entities is generally accepted, the question is, do these entities behave like "particles"? And to answer this, you must first define what "particle" means. If you just define a particle as a discreet entity, then the particle relation is trival, but is it meaningful? Probably not.
     
  16. Aer Registered Senior Member

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    Well, it made sense to whoever introduced the "standing wave" model of describing matter. Although I've never really looked into it and have only heard of it. I don't even know the qualifications of the person who came up with it (may be a crackpot?

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  17. Pete It's not rocket surgery Moderator

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    All good points, Aer. I think we're on the same wavelength

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    .
     
  18. cato less hate, more science Registered Senior Member

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    nice play on words.

    anyway, I was just saying that photons don't really need a particle like description. I mean, they give momentum, but is that just a wave giving energy to a particle, or is it really colliding with it? sure light is quantized, but does that make it a particle, or could it just be a quantized wave? I guess it is a matter of definition, I just thought my fever induced idea was worth airing.

    all 1s =]
     
  19. Aer Registered Senior Member

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    You better never post again. Hell, someone ban cato so he can't post again.
     
  20. Physics Monkey Snow Monkey and Physicist Registered Senior Member

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    It seems that everyone here pretty much accepts that light can behave like a wave, and people have suggested that 'particle' like behavior may be explainable by appealing to the notion of quantized wave. Is the alternative view possible? If I regard the photon as particle with momentum and energy which moves along a definite path, then I can via the principle of quantum superposition and the path integral reproduce all the wave like characteristics of light i.e. interference, diffraction, etc. Just as some have suggested that light is really a quantum wave that can also act like a classical particle, am I not then justified in saying that the photon is really quantum particle that can also act like a classical wave?

    I can always take plane waves and superpose them to produce a wavepacket (still tecnhically a wave) that is localized in space. Moreover, within the limits defined by the Heisenberg uncertainty principle, I can also specify the momentum of the wave. A localized object with momentum sounds like what we mean by a classical particle. The beauty of the mathematics is that it is completely reversible. What this means as that I can just as well start from my 'particle like' wavepackets and superpose them to produce the old familiar plane waves. Then waves are superpositions of particles rather than particles being superpositions of waves.

    What do you think?
     
  21. Aer Registered Senior Member

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    What? no.. light is a wave. It has frequency, wavelengths, etc.

    No. What I said has been taken completely out of context by you. I said if you defined a 'particle' as a discreet entity (i.e. quantized) then the relationship between light and particle is trivial, but I don't agree with that generalized definition for a particle.

    No.
     
  22. Physics Monkey Snow Monkey and Physicist Registered Senior Member

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    Light also has momentum, and energy. It can scatter with other particles, it can be localized to the same extent any other quantum object can, and it comes in discreet amounts. It responds to and generates gravity like any other particle. So it's a particle. There is not any beam of light anywhere in the world that has a perfectly well defined wavelength and frequency. Current lasers can, I think, be stabilized to a certain frequency within a few milli Hz these days, but the light still has a bandwidth.
     
  23. cato less hate, more science Registered Senior Member

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    it generates gravity?
     

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