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Homework Help: Please help me out with the length on this sound intensities problem

  1. Dec 4, 2008 #1
    1. The problem statement, all variables and given/known data

    When sounded separately, two identical car horns produce sound intensities at your ear in the ratio 6:1. If the nearer car is 8m from you, how far from you is the more distant car? Assume uniform spherical wavefronts.

    2. Relevant equations
    Intensity=P/4x(3.14)"pi"x R^2
    ratio fartest car=(ratio nearest car+ratio that i am)^1/2<<"squareroot"

    3. The attempt at a solution
    All I did was the surface area for the sphere, which was
    4x3.14x8^2= 1607.7
    Then i do not know what else to do because i need to find the length, I know the answer should be 19.6
  2. jcsd
  3. Dec 4, 2008 #2


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    Homework Helper

    Welcome to PF.

    I ∝ 1/r²

    So the ratio of I1/I2 = R2² /R1²

    That suggests then that

    6/1 = R²/8² then isn't it?
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