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What is Light?

  1. Nov 16, 2008 #1
    Hi,

    A friend and I have been having a long standing debate on the nature of light, being an uneducated layman I tend to stick to the conventional interpretation of wave-particle duality but my friend maintains that light is solely a wave.

    He found this link at [link to crackpot website removed - Zz.] to back up his idea. Is there any truth in this?


    Thx
     
    Last edited by a moderator: Nov 18, 2008
  2. jcsd
  3. Nov 17, 2008 #2

    russ_watters

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    I'm a little thin on the particulars, but since no one else responded....

    The "wave particle" duality by now is an outdated/introductory level explanation of the nature of light. Today, light is considered neither a wave nor a (massive) particle, but something else entirely.

    I'll confess to not reading much of the link, but at first glance, it appears to be crackpottery. That light can be quantized is critical to quantum mechanics and very well established experimentally.
     
  4. Nov 17, 2008 #3
    Wave-particle duality applies to everything. Light happens to be very wave-like because it has no mass, it still has particle qualities. Look up a list of fundamental particles. The photon will be included.
     
  5. Nov 17, 2008 #4
    Ok, I guess I should have been a little clearer.

    I thought that wave-particle duality was the theory that light was a special quantised form of matter, that acted like a particle and a wave. I know that it is neither, it just has some particle-like properties and some wave-like properties. (So what is this theory called?)

    My friend though, won't believe that, he constantly insists that light is a wave and nothing more then wave. I've tried to explain it as best I can, but I guess not very good at understanding the whole concept. He won't listen to me, my chemistry teacher, my phyisics teacher or any of the websites I've shown him. Maybe its a lost cause...

    Can anyone explain it to me, just so I can be sure I have the theory/concept right? And how does quatum mechanics explain the concept of light? I have a feeling that it something to do with string theory, but thats just a guess. Nah, that can't be right, string "theory" is just an educated guess about the nature of reality right?


    Thx
     
  6. Nov 17, 2008 #5
    You are right, except that wave-particle duality extends to everything, not just light. Your friend is obviously not familiar with quantum theory. Everything is quantized. That means particles.
     
  7. Nov 17, 2008 #6

    jtbell

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    Quantum electrodynamics (QED).
     
  8. Nov 17, 2008 #7
    Ok thx I'll look into that.
     
  9. Nov 18, 2008 #8

    ZapperZ

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    Please note that we do not allow any links to crackpot websites, per our PF Guidelines, even if one intends to disprove it.

    Zz.
     
  10. Nov 18, 2008 #9

    HallsofIvy

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    Oh, dear!

    I have a Ph.D. in mathematics with a minor in Physics and I find Quantum Electrodynamics very rough going! Be warned.
     
  11. Nov 18, 2008 #10
    What makes QED so difficult? What techniques are involved that make it hard?

    Does anyone have any good online resources on the theory?
     
  12. Nov 18, 2008 #11
    quantum mechanics. The wave-like properties arise from the probability distribution field in quantum mechanics
     
  13. Nov 19, 2008 #12
    Don't worry HallsofIvy, I don't try to understand the math I just try to understand the theory. Besides, I always remember the words of the wise person who stated that, "If you think you understand Quantum Phyisics, then you don't know Quantum Phyisics".

    Looks like my friend has given up though, he still hasn't admitted defeat yet, but he's lost interest so maybe I can finally settle this.
     
  14. Nov 19, 2008 #13

    ZapperZ

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    I think you missed an important aspect of physics. The "math" IS the theory. All theories and concepts in physics can only be described accurately and unambiguously with mathematics. The theory of classical electromagnetism is described by the Maxwell equations, for example.

    So without understanding the math, you cannot understand the theory beyond just the superficial level.

    Zz.
     
  15. Nov 19, 2008 #14
    I know that! I'm a year 11 phyisics student, I'm not even out of high school. Why would I try to understand the calculations behind quantum theory?

    Words, after all, are just another way of expressing numbers and words are much easier to understand. Does New Scentist Magazine use calculations when explaining quatum theory to laymen, no!



    No offense intended Zz.
     
  16. Nov 19, 2008 #15

    ZapperZ

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    1. The strength of the electric field falls as one moves further away from the point source.

    2. [tex]E(r) = \frac{kq}{r^2}[/tex]

    Question: which one can tell you the strength of the E-field at a particular location?

    You have also misunderstood my point. I'm not telling you to understand the mathematics. I can already tell, from the very beginning, that you have a long way to go. I am simply trying to make sure you understand that a "theory" in physics means the mathematical formulation of the concept. So if you can't understand the math, you should not make statement of trying to understand a theory without the math! That's incorrect and cannot be done beyond the superficial level.

    Our "words" have many social and human connotations. It is why it can be very vague and ambiguous. Look at how many people got the wrong impression when words such as "teleportation", "particle", etc. are used to describe certain aspects of physics. That's why "English" isn't the language of our universe.

    And "New Scientists" is a prime example of presenting physics in a superficial manner. Is there anything wrong with it as far as informing laymen? Probably not. But that layman shouldn't go around telling others that he has learned about the theory of such-and-such. Because he hasn't.

    Zz.
     
  17. Nov 19, 2008 #16
    Fine, if your just going to beat me up and act like a roborg I won't bother trying to understand.

    I'll leave it all to the wise mystics on their holy mountain. Aparrently, I'm just not good enough for scietific knowlege.
     
  18. Nov 19, 2008 #17

    ZapperZ

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    You had the opportunity to learn from an error in what you said. Instead, you took it as if someone is trying to "beat" you up.

    You'll notice that I went to great length in trying to EXPLAIN what went wrong. I didn't just say "shut up! You're wrong!". Rather than trying to figure out if there's any merit in what I've tried to explain to you, you seem to want to be defensive about it.

    I may have tried to lead you to the water, but I certainly can't force you to drink from it. So this thread is done.

    Zz.
     
  19. Nov 19, 2008 #18

    Doc Al

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    No one's "beating you up". Here's a popular book that you might enjoy: "QED: The Strange Theory of Light and Matter" by Richard Feynman. It's very readable and will give you a taste of what's going on.
     
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