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Is there something wrong with this wave concept?

  1. Feb 25, 2012 #1
    1. The problem statement, all variables and given/known data

    1. As the wavelength of a wave in a uniform medium increases, its speed will _____.

    a. decrease


    b. increase


    c. remain the same


    2. As the wavelength of a wave in a uniform medium increases, its frequency will _____.

    a. decrease


    b. increase


    c. remain the same


    2. Relevant equations

    v = λf
    f = 1/T
    v = λ/T


    3. The attempt at a solution

    1. I answered B, increase, but it says the answer is C.

    2. I answered C, because I know frequency does not change; only the wavelength changes. But then, the answer says it decreases because the wavelength and frequency are inversely proportional.
     
  2. jcsd
  3. Feb 25, 2012 #2
    Problem 2 is kind of the answer to problem 1. Since the velocity is constant*frequency*wavelength, if the wavelength goes down the frequency goes up to compensate. The wave still travels with respect to the speed of light in the medium.
     
  4. Feb 25, 2012 #3
    But I am confused at the moment because what I read is that frequency of a wave does not change, only the wavelength :|.
     
  5. Feb 25, 2012 #4
    Frequency is number of waves per second, so if the length of a wave gets smaller then more waves will fit in one second time.
     
  6. Feb 25, 2012 #5

    cepheid

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    Staff Emeritus
    Science Advisor
    Gold Member

    The wave speed is determined by the medium. So, if the medium doesn't change, the speed can't either.

    You are confused because you are thinking of *refraction* in which the wave goes from one medium to another different medium. In this case, the wave speed can change at the interface (because the medium has changed), but the frequency cannot change at the interface, becuase if it did, you would be magically gaining or losing wavefronts.
     
  7. Feb 25, 2012 #6
    Oh I get it now lol. The answer I was looking for :P. thx
     
  8. Feb 25, 2012 #7
    Yeah makes sense. thanks!
     
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