Friday 5new

# Friday 5new - Name Impedance Matching Friday 5 We have been...

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Name:___________________________ Impedance Matching Friday 5 We have been saying that if the impedance is matched between two media, then there will be no reflection of waves as energy passes from one medium to another. If a wave pulse passes from medium number 1 with impedance Z 1 and strikes a medium number 2 that has impedance Z 2 , the ratio of the amplitude of a reflected wave pulse A r to the incident wave pulse A i is given by: 21 1/ r i AZ Z Z = + Plot of the ratio A r / A i given the ratio Z 2 /Z 1 Fig. 1 Notice that if a wave reflects from a low impedance ( Z 2 less than Z 1 ) then the reflected pulse has the same sign and nearly the same amplitude as the incident pulse. If it reflects from a high impedance ( Z 2 greater than Z 1 ) then the sign is inverted. This is what we saw with reflections on the wave machine in lecture. If the impedance ratio is 1, this means that the impedances are the same and then the amplitude of the reflected wave is zero. This is called "impedance matching".

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## This note was uploaded on 03/30/2008 for the course 029 044 taught by Professor Skiff during the Spring '08 term at University of Iowa.

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Friday 5new - Name Impedance Matching Friday 5 We have been...

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