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Hertzian wave and harmonics

  1. Apr 25, 2008 #1
    A high voltage capacitor is charged and then the two leads are shorted together generating a spark, simultaneously a nearby radio crackles. This shows us that when the spark was generated radio waves was also generated. These primitive radio waves are sometimes called hertzian waves. A bolt of lightning also generates hertzian waves.

    My question is about the nature of the waves produced. When a bolt of lightning strikes the ground dose it produce a predominant frequency wave along with its harmonics?

    Let me explain with an analogy, a stretched wire when plucked produces a fundamental pitch but simultaneously pitches are produced which are harmonic multiples of the fundamental pitch. If a stretched wire produced a fundamental pitch of 100hz then it will also produce pitches of 200, 300, 400hz etc

    When a hertzian wave is produced dose it also have a fundamental wavelength along with harmonics which are multiples of the first?
     
  2. jcsd
  3. Apr 25, 2008 #2

    Andy Resnick

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    A spark will act as an impulse, generating a wide bandwidth. The properties of the medium in which the waves propogate will attenuate some frequencies more than others, so the long-time behavior will result in the appearance of resonant frequencies (Schumann resonances, for example).

    Here's a fun website- audio recordings of the "audio" portion of the EM spectrum during thunderstorms:

    http://www-pw.physics.uiowa.edu/mcgreevy/
     
  4. Apr 25, 2008 #3
    Thanks for the info Andy......it still leaves my question unanswered though:biggrin:
     
  5. Apr 28, 2008 #4
    i think he did in the first line...

    all frequencies are available in the impulse response....and generally are of the same magnitude.....
    the resonances (schumann) he described are the resulting peaks of atmospheric filtering....because of the size of the cavity namely height from land to top of atmosphere and space around the earth.......the rest are absorbed more quickly....
     
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