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Intensity of the superposition of sound waves

  1. Dec 5, 2009 #1
    1. The problem statement, all variables and given/known data
    A sound wave with intensity 4 mW/m2 interferes destructively with a sound wave that has an intensity of 10 mW/m2. What is the intensity of the superposition of the two?

    2. Relevant equations

    sqrt of both values

    3. The attempt at a solution
    i believe that taking the sqrt of both values then adding them then squaring them is the correct solution but i keep getting the incorrect answer.

    i keep getting 26.65
  2. jcsd
  3. Dec 5, 2009 #2


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    Homework Helper

    Why are you adding? The question says that the interference is destructive.
  4. Dec 5, 2009 #3
    ok so what exactly do i do then?
  5. Dec 5, 2009 #4


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Subtract, don't add, since the interference is destructive.
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