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Ultrasound - intensity reflection coefficiant calculations

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Mar6-12, 11:39 AM
P: 30
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....
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