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Homework Help: Constructive interference

  1. Jul 28, 2014 #1
    1. The problem statement, all variables and given/known data

    Two speakers A and B, sends out sounds at 400 hz

    In what distance x between speaker A and the point P is it constructive interference ?


    2. Relevant equations

    λ = 2ΔL/(2p-1),

    v = 340 m/s

    f = 400 Hz

    3. The attempt at a solution

    λ = 2ΔL/(2p-1),

    λ = 340/400 = 0.85 m <==>

    lowest constructive interference p = 1

    0.85 m = ΔL <==>

    0.85 = y - x, where y = (2.5)^2+x^2=y^2 is the distance between P and B.

    Is this right ?
  2. jcsd
  3. Jul 28, 2014 #2


    User Avatar
    Science Advisor

    That should get you a constructive interference point (node).
    I don't think the nearest node to A (i.e., smallest x) occurs for p = 1, though.
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