Answer
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 = $200\times7.5\times10^{-5}m=1.5\times10^{-2}m$
