College Physics (7th Edition)

Published by Pearson
ISBN 10: 0-32160-183-1
ISBN 13: 978-0-32160-183-4

Chapter 14 - Sound - Learning Path Questions and Exercises - Exercises - Page 523: 9


a). $7.5\times10^{-5}m$ b). $1.5\times10^{-2}m$

Work Step by Step

Medical ultrasound uses a frequency of around 20MHz to diagnose human conditions and ailments. a). Speed of sound in tissue = 1500m/s f=20MHz So, smallest detectable length is the wavelength. So, wavelength = $\frac{1500}{20\times10^{6}}$ Wavelength =$7.5\times10^{-5}m$ b). 200 times the wavelength is the penetrable depth. Penetration depth = $200\times7.5\times10^{-5}m=1.5\times10^{-2}m$
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