P18_070

# P18_070 - = R − 1 v R 1 cos θ = 0 90 m s where v = 1540 m/s θ = 20 ◦ and R = 1 5495 5 × 10 6(c We interpret the question as asking how ∆

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70. (a) The blood is moving towards the right (towards the detector), because the Doppler shift in frequency is an increase :∆ f> 0. (b) The reception of the ultrasound by the blood and the subsequent remitting of the signal by the blood back toward the detector is a two step process which may be compactly written as f +∆ f = f µ v + v x v v x where v x = v blood cos θ. If we write the ratio of frequencies as R =( f +∆ f ) /f , then the solution of the above equation for the speed of the blood is v blood
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Unformatted text preview: = ( R − 1) v ( R + 1) cos θ = 0 . 90 m / s where v = 1540 m/s, θ = 20 ◦ , and R = 1 + 5495 / 5 × 10 6 . (c) We interpret the question as asking how ∆ f (still taken to be positive, since the detector is in the “forward” direction) changes as the detection angle θ changes. Since larger θ means smaller horizontal component of velocity v x then we expect ∆ f to decrease towards zero as θ is increased towards 90 ◦ ....
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## This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.

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