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Homework Help: AM/FM Radio Waves & Diffraction

  1. Apr 17, 2010 #1
    1. The problem statement, all variables and given/known data

    Typical AM radio waves usually have a frequency between 540 kHz and 1400 kHz. FM radio waves tend to have frequencies between 89 MHz and 105 MHz. Both types of waves travel at the speed of light. In terms of diffraction, use this information to help explain why in many low lying valleys in mountainous regions, AM reception is much clearer than FM reception.

    2. Relevant equations


    3. The attempt at a solution

    Well, I'm not so sure. I know that the FM waves obviously have a higher frequency so I am guessing that the answer lies somewhere there. Could someone give me the jump-start that I need to get going on this question? Thanks a lot!
  2. jcsd
  3. Apr 17, 2010 #2
    try to explain it in terms of wavelength ..
  4. Jun 5, 2010 #3
    I assume it is because of that am relies on amplitude and fm relies on frequency.
    Last edited: Jun 5, 2010
  5. Jun 5, 2010 #4
    The key word is in your title..."diffraction".What is diffraction and which of the two waves diffract the most?
  6. Jun 7, 2010 #5
    OK. this is why, FM radio broadcasts travel at a thing called "straight line". Thus they pretty much only travel at straight lines (Sort of, but you get the picture) so if anything like a mountain or a wall comes in its way it will be interfered. But AM doesn't do this, it travles around the mountain or wall. But they have invented a thing called digital radio. This is better quality to FM and has better signal. It is the same as digital television (if you know what that is).
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