An ultrasonic wave has a frequency of 1.5 MHz. What is its wavelength in water if its speed is 1498 m/s?

Question

An ultrasonic wave has a frequency of 1.5 MHz. What is its wavelength in water if its speed is 1498 m/s?

Answer 1

wavelength = speed/frequency

1498/(1.5*10^6) = 9.99*10^-4m

Answer 2

About one millimeter...

v (velocity) = 1498 is about 1.5 x 10^3 m/s

f (frequency) = 1.5 x 10^6 Hz

Wavelength is v / f

1.5 x 10^3 / 1.5 x 10^6 = 1 x 10^-3 = 1 millimeter

Common medical ultrasound imaging is done at a frequency of about 4 MHz, so the wavelength is about 1/3 millimeter, giving doctors pretty good resolution of the objects being imaged.