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What's wavelength exactly?

  1. Sep 2, 2013 #1
    Dear people,i wanted to know wat actually is wavelength??
    I have heard all the definations most of them says its difference
    bw two crest or trough..that is ok.most of the people understand
    wavelength as path of particles while travelling..is it true??

    wat is meant by wavelength of protons and electrons???
  2. jcsd
  3. Sep 2, 2013 #2
    The wavelength of electrons (or matter particles in general) is de Broglie wavelength, which is defined as λ = h/p.
  4. Sep 2, 2013 #3
    What do you mean by that? Wavelength is not a path of particle. Wavelength is the length of a wave: the distance between 2 subsequent crests. It has nothing to do with the path of the particle.
  5. Sep 2, 2013 #4
    Im not asking defination or taughtformulaes..but meaning...
  6. Sep 2, 2013 #5
    Howcould u explain wavelength to a new one?? Explain clearly wat wavelength is ...how electrons travel in electron microscope
  7. Sep 2, 2013 #6

    Vanadium 50

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    I don't think people understand what you are saying. It would be helpful (and be consistent with the PF Rules) if you were to drop the text-speak and write in complete sentences.
  8. Sep 2, 2013 #7
    I'm still not sure I understand your question. Wavelength is just the distance between 2 crests. There is no deeper mystery behind that and it's not possible to explain it more clearly. Maybe showing the image.

    Or are you asking about the wavelength of an electron? Well, electrons are excitations (waves) in a quantum field. So there is a field (something that has a value in every point of 3D space) and there is a wave in that field. This wave has a wavelength. It is of course much more complicated wave than a simple sine, because it is in 3D and the field value is not a real number. It is very difficult to visualize, but maybe you will find helpful this animation of a wavepacket.

    This can be understood as a very simplified animation of an electron wave. The wavelength is the distance between the 2 crests. The electron is the whole wavepacket, traveling in straight line.
    Last edited: Sep 2, 2013
  9. Sep 2, 2013 #8
    Waves are often represented like the example links above - something is varying "up and down" from the center line, and the distance between adjacent up peaks, down peaks, or any congruent parts of the wiggling line may be used to define the wave length.

    This can be confusing because we are familiar with water waves where the surface does move up and down.

    Your question seems to be, "What is wiggling?" in the sense of "What is actually moving?"

    The representations show a variation in a value by graphing the value "up and down" on the graph... but that is the "mathematical" view. The vertical axis does not have to represent lateral motion of the thing - it might be density, or temperature, or color, or some other abstraction that has no physical correspondence to a gross movement.

    So, the value wiggling up and down on the graph does not necessarily imply that there is a physical thing actually moving up or down or making an actual wiggling motion with respect to the center line - it is just a way of showing the changing value of something (something that does not have to really move physically to change value).

    If I graphed how bright it is outside for a week I would get an overall wiggly line that had a wavelength of one day and there would be seven periods of that wavelength. You would not ask "What is wiggling?" in the sense of a cyclic motion back and forth about that when you knew that the measure was of brightness... right? The brightness changes value without moving... the crests and troughs have a vertical distance between them - that is how they are defined and located on the graph for measuring the wavelength between crests or between troughs, but that vertical component of an artifact of the graphical representation. In the brightness example, the brightness is certainly not "moving up and down" as a physical motion.
  10. Sep 3, 2013 #9
    Wen we say that e have wavelengths..so does we actually mean that the electric field produced by them have this wavelength as assigned to electron?
  11. Sep 3, 2013 #10

    Yes, that's how your car stereo picks up different radio stations.
  12. Sep 3, 2013 #11


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    The de Broglie wavelength of an electron is unrelated to the wavelength of the electromagnetic waves that may or may not going on in the general neighborhood of the electron.
  13. Sep 3, 2013 #12
    In short, electrons can behave as electromagnetic fields or as localized particles. Or as matter particles. Since you already asked this and didn't get an answer, there is no classical analogy about the behavior of elementary particles. It's basically all fields and their manifestations as classical matter. There is no deeper understanding than this at this point, I am afraid.
  14. Sep 4, 2013 #13


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    ankit.jain asked:
    "Howcould u explain wavelength to a new one?? Explain clearly wat wavelength is ...how electrons travel in electron microscope"

    When electrons pass through the material they produce diffraction patterns; by using Bragg's law and the parameters of the diffraction pattern you can determine the wave length of the electrons. This wavelength is consistent with the de Broglie formula.

    Perhaps your question is "what is waving"? In that case the answer is "I don't know".
  15. Sep 4, 2013 #14
    When annihilating electrons, or producing electron-positon pairs in photon collisions, the wavelengths of the electrons and photons are indeed related. They are not equal due to mass difference between photons and electrons, but they're directly related by a simple equation.
  16. Sep 4, 2013 #15
    Cant understand sir
  17. Sep 4, 2013 #16


    Staff: Mentor

    ankit.jain. Wavelength is the distance between two crests of a wave. That is it. There is no simpler explanation possible.

    I believe that you have a different question. Please spend some time to write a clear question in correct English so that people can understand the issue you are having. Your current questions are too vague and sloppy to answer. It is wasting everybody's time, and, as you can see, there are many members who want to help if you can communicate what you really want to know.
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