Question

Dolphins swimming underwater rely upon echolocation to be able to locate nearby objects. While underwater, a dolphin produces an ultrasonic sound with a frequency of 115 kHz. What is the wavelength of this sound? If, while stationary in these waters, the dolphin emits a sound pulse and receives an echo after 0.260 s, how far away must the reflecting object be from the dolphin? Take the speed of sound in ocean water to be 1530 m/s. Answer both wavelength and distance in m.

Answer 1

relation ship between Speed V , frequency f and Wavelength L is

V = Lf

so

here

speed of ultrasonic sound in sea water at 20 C = V = 1530 m/s

frequency = f = 115 kHz = 115000 Hz

wavelength L = V/f = 1530/115000 = 0.0133 m

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Speed of sound in water at 20 C = 1530 m/s

Time period of travel = 0.26 sec

as Distance S = V t

total distance covered by the sound = S = 1530* 0.26 = 397.8 m

distance hiere = half the total distance travelled

so D = d/2 = 397.8/2 = 198.5 m