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Homework Help: Electromagnetic Spectrum Problem Help

  1. Oct 23, 2008 #1
    1. The problem statement, all variables and given/known data
    As you drive by an AM radio station, you notice a sign saying that its antenna is 112m high. If this height represents one quarter-wavelength of its signal, what is the frequency of the station?

    2. Relevant equations
    c (speed of light) = f (frequency) x d (wavelength/lambda)

    3. The attempt at a solution
    It's simply the wording that's messing me up. What I did was multiply 112 meters by 4 since it says that the height represents one-quarter of the wavelength, and simply divided the speed of light by that number to get an answer of about 6.70 x 10^5 Hz. I know radio waves at their smallest are generally 10^6 Hz. Any comments? Any help is greatly appreciated
  2. jcsd
  3. Oct 23, 2008 #2


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    Homework Helper

    Check your units and make sure C is in m/s not km/s.
  4. Oct 23, 2008 #3
    I made sure that C = 3 x 10^8 m/s, so the answer I obtained came from 3 x 10^8 / (112 x 4) = 6.70 x 10^5 Hz (rounded up to 3 sigfigs). Thanks though.
  5. Oct 24, 2008 #4


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    Looks good. AM frequencies are about 500 to 1600 kHz, or around 10^6 Hz as you pointed out.
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