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Homework Help: Interference of two radio waves

  1. Jun 2, 2009 #1
    1. The problem statement, all variables and given/known data

    Two coherent sources of radio waves, A and B, are 5.00 meters apart. Each source emits waves with wavelength 6.00 meters. Consider points along the line connecting the two sources.

    At what distance from source A is there constructive interference between points A and B?

    2. Relevant equations

    Let P be the point of constructive interference:

    [tex]r_1 - r_2 = m\lambda [/tex] where [tex]r_1 [/tex] is the distance from A to P and [tex]r_2[/tex] is the distance from P to B.

    These were the hints given, and don't make sense.

    3. The attempt at a solution

    I got the answer of 2.5 metres by drawing a diagram and estimating where the two waves would cross (constructive interference). The answer was correct, a lucky guess...

    I don't know how to apply that equation. Does it need to be applied twice? For m I would use the value of 1?
  2. jcsd
  3. Jun 2, 2009 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    m could be any integer, not just 1.

    Try m = 0 or 1, and see what you can come up using your equation,

    r1 - r2 = m λ
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