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Plane waves, phase difference question

  1. Oct 13, 2009 #1
    1. The problem statement, all variables and given/known data

    Consider a lightwave having a phase velocity of 3 x 10^8 m/s and a frequency of 6 x 10^14 hz. What is the shortest distance along the wave between any two points that have a phase difference of 30 degrees ? What phase shift occurs at a given point in 1 microsecond and how many waves have passed by in that time ?

    2. Relevant equations

    velocity = frequency x wavelength

    3. The attempt at a solution

    have calculated that the wavelength is 5000m, by dividing speed of light by the frequency, but am stuck and don't know how to proceec. any help would be amazing, thank you!
  2. jcsd
  3. Oct 13, 2009 #2


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    Homework Helper

    When the distance between the two points is equal to the wavelength, the phase difference between the points is 2π. So when the phase difference between the two points is π/6, the distance between the two points is.....
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