(a) Calculate the wavelengths in air at 20 C for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz. (b) What is the wavelength of a 10-MHz ultrasonic wave?

Answer 1

speed = wavelength x frequency or wavelength = speed / freq

for f = 20Hz, wavelength = 343m/s / 2.0 x 10^1 Hz = 17.2m

for f=20,000 Hz, wavelength = 343m/s / 20,000Hz = 0.017 m

39MHz = 39x10^6 Hz so wavelength = 343m/s / 39x10^Hz = 8.8x10^-6 m