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Fourier Transform Question - Negative Frequencies?

  1. Feb 24, 2009 #1


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    When I see a graph of a Fourier Transform, or something in the frequency domain, say band-limited from -[tex]\Omega[/tex] to [tex]\Omega[/tex], I'm confused to what the interpretation is of the negative frequencies. Physically it would seem as though something considered in cycles/second for example, should be positive but mathematically the FT will allow for negative frequencies.

    Can somebody clarify this for me?
  2. jcsd
  3. Feb 24, 2009 #2


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    [tex]e^{-\omega ix}= e^{\omega (-i)x}[/tex] so negative frequencies are just the complex conjugate of the positive frequencies.
  4. Feb 24, 2009 #3
    Hadn't really thought about it. Physically positive/negative frequencies could be interpreted as left/right circularly polarized waves.
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