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Combining high frequencies to get a large frequency

  1. Dec 29, 2006 #1
    "Combining high frequencies to get a large frequency"

    "Combining high frequencies to get a large wavelength"

    Is this possible? There will be constructive and destructive interference, but can there be anything that increases the wavelength?
     
    Last edited: Dec 29, 2006
  2. jcsd
  3. Dec 29, 2006 #2
    What is a "large" frequency?
     
  4. Dec 29, 2006 #3

    DaveC426913

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    I think he means "to get a low frequency" and "anything that increases wavelength".
     
  5. Dec 29, 2006 #4
    Ya... that's what i meant ... dunno why i didn't see that =p
     
  6. Dec 29, 2006 #5

    disregardthat

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    Well, do 2 waves interact with eachother if they meet? And if they do, in what level?
     
  7. Jul 1, 2008 #6
    Re: "Combining high frequencies to get a large frequency"

    Yes it is and its quit common. Radios use this to bring rf frequencies down to audio f. Piano tuners use this to tell when they're approaching the right string tension. Pilots use it to sync up twin engines on boats and planes. It's call a beat frequency. I bet wikipedia.org has something on it. take a look.
    alex
     
  8. Jul 1, 2008 #7
    Re: "Combining high frequencies to get a large frequency"

    The technique is referred to as heterodyning.
     
  9. Jul 1, 2008 #8

    Andy Resnick

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    Re: "Combining high frequencies to get a large frequency"

    Heterodyning is also beginning to be applied to microscopy, to move spatial frequencies beyond the classical resolution limit back into the exit pupil. One way is off-axis illumination, but there are several:

    Proc Natl Acad Sci U S A. 2005 Sep 13;102(37):13081-6. "Nonlinear structured-illumination microscopy: wide-field fluorescence imaging with theoretically unlimited resolution.", Gustafsson MG.
     
  10. Jul 1, 2008 #9
    Re: "Combining high frequencies to get a large frequency"

    Interesting..
    When coupling a fiber-optic bundle image transfer block to a fibre-optic faceplate on an image intensifier, we used to rotate the part to a place where the Moire patterns and other effects were minimum.

    I noticed once that as the planes of fibres came to line up with the faceplates (bundles of hexagons) structure, I could make in the interference patterns, a clear image of the boundaries, including broken interfaces and distorted joins. Also, I could get several versions of these, getting bigger as I approached "zero beat".

    This was about 15 years ago. I wondered at the time whether the effect could be used for microscopy, and now, whether what I saw is part of this.

     
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