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The Speed of Light

  1. Mar 21, 2006 #1
    I was having a little trouble understanding a concept in my book. My book asked the following question:

    The frequency of electromagnetic wave A is twice that of electromagnetic wave B. For these two waves, which is the ratio wavelengthA/wavelengthB of the wavelengths in a a vacuum?

    The answer turned out to be that the ratio would equal 1/2 because both waves have the same speed. I was able to calculate the 1/2 in my ratio, but I didn't understand how both waves would have the same velocity. I know frequency * wavelenth = velocity. If frequency is twice as large in one wave, how can they have the same speed?
  2. jcsd
  3. Mar 21, 2006 #2


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    Frequency * wavelength = velocity.

    If velocity is fixed, then doubling frequency requires halving wavelength. That's what the question wanted you to realize.

    - Warren
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