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Another Electromagnetic wave question

  1. Jun 8, 2004 #1
    This one doesn't make sense to me.

    A lost person may signal by flashing a flashlight on and off using morse code. This is actually a modulated EM wave. Is it AM or FM? What is the frequencey of the carrier, approximately?

    How can a light wave be AM or FM? I don't get it.
    I thought the answer was AM though.
  2. jcsd
  3. Jun 9, 2004 #2


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    Yes, it's AM- though you are right- it's a stretch to call it "AM" or "FM"! "AM" means "amplitude modulation": you create the signal by changing (modulating) the amplitude (strength) of the signal. "FM" means "frequency modulation" where you change the frequency of the signal. The frequency of light is what determines the color and you can't change that. By flashing the light on and off you are changing the amplitude: full strength and 0. The "frequency of the carrier" is the frequency of the the light- probably close to that of yellow.
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