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ANOTHER Theory of light

  1. Feb 3, 2004 #1
    Light, what is it? the most up to date theories I have read claim that it is both a particle and a wave (wave/particle duality). How can something that obviously has a physical existance be two things? I agree that in certain situation light behaves as a photon and in others as an EM wave but why is there not one model of light that can predict both of these? I propose that they is. Since my theories are usually overly complex i'll summerise it here and if anyone is interested i can elaborate further.

    Light IS a partical, infact not just light but all electromagnetic radiation consists of photons. These photons are emitted by electrons when they change energy levels within an atom. For a photon to exist it must have mass (no matter how small) and it is generally accepted that photons have no charge. However, if a photon has no net charge but does have a positive and negative side to it, as the photon departs from the electron its possitive side would remain pointing towards the negative electron (only for a very short period of time). This would cause the photon to spin. The spin would be proportional to the magnitude of its charges which would be proportional to its mass. The frequency of a photon is also proportional to its mass so provided the proportionalities are the same (which can be shown if some basic assumptions are made) then the angular frequency of the photon is equal to its observed EM frequency. This can be used to explain how photons can be observed to behave like waves. it will take a particular distance for a photon to rotate through 360* (this is its wave length). If a pair of photons arrive at an atom facing opposite directions (ie, out of phase) then the one with possitive facing forewards would hit an electron, and the negative one would hit the nucleas, the effect of this is that the charge between the electron and nucleas is unchanged and therefor the electrons energy is unchanged and so no photon is re-emmited, this is observed as deconstructive interference.

    Started as a summary but went into a bit more detail (appologises for the tedium). Personally I cant see anything wrong with my theory, but i'm obviously biased so I would appreciate critisism (and praise if any is deserved) from anyone who is interested.
     
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  3. Feb 3, 2004 #2

    FZ+

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    How would this explain the twin slit experiment, where the photons arrive one at a time?
     
  4. Feb 4, 2004 #3
    It was my belief that photons arriving at one point from each slit arrived together. If light is thought of as a wave then the out of phase points on the wave must arrive together, so surely the photons must also
     
  5. Feb 4, 2004 #4

    russ_watters

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    The statement that photons have mass needs to be substantiated with physical evidence.
     
  6. Feb 4, 2004 #5
    Photons have momentum so how can they not have mass? ofcourse they dont have much mass but they must have some. I always thought that the photoelectric effect was proof enough that photons had mass, how can something that is massless knock an electron out of its orbit? Also, when photons are absorbed and re-emitted inside dense mediums surely a massless particle could travel in the gaps between electrons and the nucleas (atoms being mostly made up of nothing), but if they have mass then they can have a force applied to them by either the electron or nucleas in order to change their path
     
  7. Feb 4, 2004 #6

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    Uh... I think you have the wrong conception of such ionisation here. It is not a real billiard ball style collision. And things with momentum can have no mass.

    But then, a great majority of other photons must also have arrived in no pair at all. If we are to presume these all register as hits, this would not reproduce the interference pattern we see. There would simply be no empty patches.
     
  8. Feb 5, 2004 #7

    russ_watters

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    Thats a very common misunderstanding about how light works. Simply put, light energy isn't the same as kinetic energy.

    Consider this:
    Does sound have energy?
    Does sound have mass?
     
    Last edited: Feb 5, 2004
  9. Feb 5, 2004 #8
    Russ,

    Does the photon have potential energy?

    Is energy conserved when the small amount of energy it takes to make a sound moves from mouth to rarefactions and condensations?

    I had read that 10,000,000 people's voices together would equal the energy running a flashlight.


    LPF
     
  10. Feb 5, 2004 #9
    I would say that if light is thought of as a particle it can not be associated with sound. However sound does have mass, just because that mass isn't moving in a straight line doesn't mean it has none, if you measure a sound wave impacting on a surface then surely there will be a certain mass of air which is hitting the surace?

    Light cannot behave like sound because sound propogates through a sea of atoms in the form of compressions and rarefactions, if light is a form of wave what does it propogate through?
     
  11. Feb 5, 2004 #10

    russ_watters

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    Potential energy is mass times height. So, no.
    I'm not exactly sure what you mean here - but since air is not an ideal gas, there are energy losses in the transmission of sound.
    Air has mass, but a sound wave itself does not - over what volume (size) would you measure the mass of the "sound"? A guitar string transmits sound to the air (and to the pickup) - is the mass of the guitar string the mass of the sound? Would a loud sound have more mass than a soft one? Since the air that strikes your eardrums isn't the same air that left the surface of a drum (for example), which is the one you measure the "mass" from?

    Similarly, light is not a particle and does not have mass. Light is modeled as a wave/particle entity, but thats just a model.
     
  12. Feb 5, 2004 #11
    What i mean is not that a sound wave has mass, but sound that hits a surface does. For a constant frequency of sound there will be a particular kinetic energy transfered into a surface by a sound wave, this is due to the mass of the atom and its speed at the time of impact. Sound does not have mass its own mass, but at the point of impact it does have kinetic energy which means it must have mass (possibly proportional to the frontal area of the wave)

    If light it to be modelled as a wave what does it travel through? Sound waves rely on the transmittion of kinetic energy from moelcule to molecule in order to advance, how do light waves advance?
     
  13. Feb 5, 2004 #12
    Owen,

    I hope you don't mind me inserting a qustion or two, they are related to your thread. Maybe the answers can help both of us.


    A sound wave is a pulse through a medium, like an ocean wave. If you were to put red dye in the water, it would bob up and down, but not be carried by wave as it went by. A sound wave uses the mass of air as a medium, but they stay stationary (air molecules). The vibration you feel from sound (like speaker box) is resonance from the air vibration rate and the woods' (or?) rate (density state change) as the pulse moves through. I don't know if this is exactly correct. I had never thought of a mass and sound relationship.

    Russ,

    I understand the lifting of an object with mass to a height gives it potential energy, maybe my misunderstanding is in the photoelectric effect? Does light transfer energy to the electron in this?

    Or maybe from infra-red portion of wave causing heat - is that a kind of energy?

    LPF
     
  14. Feb 5, 2004 #13

    russ_watters

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    Yes and yes. Photons give energy when absorbed and infrared light is radiated thermal energy - and thats the point. Energy in photons is not kinetic or potential beccause it has no mass. But it is energy nonetheless.
     
  15. Feb 5, 2004 #14

    russ_watters

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    You are correct. Sound waves travel through air which has mass, so there is kinetic energy transferred that way. But the mass is there before the sound goes through and stays after the sound - its not a part of the sound.

    Light is modeled as a wave, but the medium is where the analogy with sound breaks down. Light doesn't travel over a medium. Essentially it is its own medium.
     
  16. Feb 5, 2004 #15
    Russ,

    So the third kind of energy is just "regular"?

    Is this from Classic, Quantum, and Relativity viewpoints?

    (I'm trying to use the right energy with the right equations)


    LPF
     
  17. Feb 6, 2004 #16
    If light is its own medium then surely the idea of emission and absorbtion of photons is all wrong. Surely this is going back to the idea of an ether, or in this case a mass of photons floating about in space. When an atom loses energy it sends a wave through these photons, at the point where this wave is detected it will be seen to have both wave like properties and kinetic energy. This view does seem quite plausible but it was my understanding that the idea of an ether is almost universally seen as incorrect, any thoughts?
     
  18. Feb 6, 2004 #17

    russ_watters

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    THIS might be helpful. Mechanical energy and light energy, aka "radiant" or "electromagnetic" energy are only two of 6 types of energy.
    And be very careful that you don't apply the wrong equation to the wrong type of energy. For example, people have used the mechanical energy equations to calculate that light should have mass. But you can't do that because mechanical energy equations only work for mechanical energy.
    Ether is now seen as unnecessary, but the particle/wave duality doesn't depend on it anyway. Also, the photon is the "particle" of light itself, not a medium for carrying it.
     
  19. Feb 6, 2004 #18
    This theory is getting more complex than I intended, rather than looking for a model for light why shouldn't we try and look for what light is. What I mean is, light does behave like both a particle and a wave, but surely it has to be something and cant be both. A spring can behave like a wave (when oscilating under simple harmonic motion) but although in that situation it can be modelled as a wave it is still a spring. Just because light behaves like a wave doesn't mean it is, and treating it as a wave doesn't get any closer to finding out what it really is
     
  20. Feb 6, 2004 #19

    russ_watters

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    Au contraire. Since it behaves like a wave in many cases, it must be treated like one in appropriate situations, otherwise we have no way to predict how devices that depend on its wave properties will work. How, for example, are you going to get new eyeglasses made if you're not allowed to model light as a wave?
     
  21. Feb 29, 2004 #20
    What a great disucssion... I cant help adding my opinion..

    Light THeory, like all things, is being explained by humans.
    This means we are forced to try to use existing familiar concepts.
    Unfortunately, humans arent very good at understanding things that dont have an easy analogy with some other sensory or mental experience. The closest experience we have for light is either particle or wave, our tendancy is to want it(model) fit neatly into one theory/analogy.

    I think the argument of "what is light (P or W) ?" is mostly irrelevant. Whats important is that we use consistent and agreed ways of expressing its ACTUAL behaviour - partical or wave..
    When trying to <i>explain</i> light, I personally tend to favour the wave model... because I feel that expressing the fact that light energy is probablistically distributed in space is more important, and more accurate for most technically precise applications.
    I suspect that its probably easier to consequently treat electrons (and all sub-atomic particles) in the application as waves too.
    The same can go for the debate over whether it has mass.
     
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