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Homework Help: Ultrasound - intensity reflection coefficiant calculations

  1. Mar 6, 2012 #1
    1. The problem statement, all variables and given/known data

    The following table gives some specific acoustic impedances
    Tissue or Medium Specific acoustic impedance
    Air 0.00044 x 10^6
    Fat 1.38 x 10^6
    Water 1.5 x 10^6
    Brain 1.58 x 10^6
    Blood 1.59 x 10^6
    Muscle 1.6 x 10^6
    Bone 6 x 10^6

    this was in a table, when pasted it squashes it together, not sure how to get around that sorry.

    Calculate the intensity reflection coefficient, a, for the boundary between blood and muscle



    2. Relevant equations

    R = Ir/Io = (Z2 – Z1)2 / (Z2 + Z1)2

    R = reflection coefficient
    Ir = Reflection intensity
    Io = incident intensity
    Z1 = acoustic impedance 1
    Z2 = acoustic impedance 2


    3. The attempt at a solution

    Z2 – Z1 = 1.6 x 10^6 – 1.59 x 10^6 = 10,000
    Z2 + Z1 = 1.6 x 10^6 + 1.59 x 10^6 = 3,190,000

    10,0002 = 1x10^8
    3,190,0002 = 1.01761 x 10^13

    1x108 / 1.01761 x 10^13 = 9.826947455 x 10^20

    R = 9.83 x 10^20

    id just like someone to look over this for me please and make sure im doing this correctly as i really dont understand it and we havent been taught very well. we were kinda given the equasion and told to go away leaving me with no confidence at all. i wasnt sure whether you do the largest number - the smallest or the direction of the transition like blood/bone would be blood into bone or what....
     
    Last edited: Mar 6, 2012
  2. jcsd
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