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Homework Help: Wave Interference Problem

  1. Jan 19, 2014 #1
    1. The problem statement, all variables and given/known data
    A beach comber walking along the top of a sea wall notices that the waves reflecting off of the concrete breaker are creating a pattern of interference with the original incoming waves. A few meters from the breaker the waves are at maximum oscillation with a time between peak and trough of 2.4 seconds. Exactly 3.2m further to sea, there is virtually no vertical change in the water's motion. What is the length and velocity of the waves?

    2. Relevant equations


    3. The attempt at a solution
    So I'm not sure if I'm completely misinterpreting this but I'm thinking it forms a standing wave pattern and the first node is 3.2m away from the antinode so 3.2m x 4 = a wavelength of 12.8m and then v=(4.)(12.8m)(1/4.8)= 2.7m/s
    Did I do it right or am I completely off?
    Last edited: Jan 19, 2014
  2. jcsd
  3. Jan 19, 2014 #2

    Simon Bridge

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    That sounds reasonable to me.

    The distance between max and min is 3.2m ... separation of consecutive maxima is 6.4m.
    Which would represent a path difference of a single wavelength.
  4. Jan 19, 2014 #3
    Oh wait. 2.4 s is the period not the frequency.
  5. Jan 19, 2014 #4

    Simon Bridge

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    That makes a difference yes ;)
    You only need to relate the period of the standing wave oscillations to the speed and wavelength of the two travelling waves that make it.
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