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Homework Help: Fundamental frequency

  1. Mar 1, 2010 #1
    Fundamental frequency!!

    1. Ultrasound with a frequency of 4.079 MHz can be used to produce images of the human
    body.If the speed of sound in the body is the same (1.97 km/s) as in salt water, what is the
    wavelength in the body?
    Answer in units of m.

    and

    2. On a day when the wind is blowing 49.5 km/h from east to west, a fire engine
    moves toward you from the west at 112 km/h and you are heading toward the fire engine at
    94.6 km/h. If the fire engine has a 587 Hz siren and the speed of sound is 340 m/s, what frequency do you hear?
    Answer in units of Hz.
    i converted them to m/s. (340-12-30.2777)*1170/(340-12-30.27777) but i think i did it wrong. idk. grr
    and i DO NOT know how to do number 1
    plz help!!
     
  2. jcsd
  3. Mar 1, 2010 #2

    Delphi51

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    Homework Helper

    Re: Fundamental frequency!!

    The relationship between frequency and wavelength for any wave is
    v = f*λ
    That should take care of the first question.

    What is your formula for the Dopplar effect in #2? The pattern of those numbers doesn't look quite right.
     
  4. Mar 1, 2010 #3
    Re: Fundamental frequency!!

    for number 1, we're trying to find distance arent we? not velocity.
    and for 2, well i converted km/h to m/s.
     
  5. Mar 1, 2010 #4

    Delphi51

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    Homework Helper

    Re: Fundamental frequency!!

    Yes, so solve the formula for λ.
     
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