9. (a) Using λ = v/f , where v is the speed of sound in air and f is the frequency, we find λ=
343 m/s = 7.62 × 10−5 m . 4.5 × 106 Hz
(b) Now, λ = v/f , where v is the speed of sound in tissue. The frequency is the same for air and tissue. Thus λ = (1500 m/s)/(4.5 × 106 Hz) = 3.33 × 10−4 m.