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Homework Help: Help with a Wave Intensity Problem

  1. Nov 29, 2007 #1
    [SOLVED] Help with a Wave Intensity Problem

    Hello all, here is a problem that relates to Wave Motion, more specifically Wave Intensity I believe:

    The figure shows two observers 20m apart on a line that connects them and a spherical light source.
    Figure: (The best I know to do)

    (Person A)<----------20m----------->(Person B)<----------?m---------->(Light Source)

    If the observer nearer the source measures a light intensity 45 % greater than the other observer, how far is the nearer observer from the source?

    Relevant Equations:
    I = [ latex ] \frac{P}{(4pi(r^2))} [ /latex ]

    My initial thought was to state the following:
    Ia = .45Ib and da = x +20 and db = x

    Then plug in all the values given, the P's cancel, and I thought I'd be left with an answer. I got 41m, apparently that isn't right. I've been working on this problem for nearly an hour and a half.

    Any suggestions?
    Last edited: Nov 29, 2007
  2. jcsd
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