Question

Dolphins of the open ocean are classified as Type II Odontocetes (toothed whales). These animals use ultrasonic "clicks" with a frequency of about 55 kHz to navigate and find prey. You may want to review (Pages 465 - 467). Suppose a dolphin sends out a series of clicks that are reflected back from the bottom of the ocean 55 m below.

a) How much time elapses before the dolphin hears the echoes of the clicks? (The speed of sound in seawater is approximately 1530 m/s.)

b) What is the wavelength of 55 kHz sound in the ocean?

Answer 1

Part A.

given that dolphin sends out clicks which are reflected back from the bottom of ocean 55 m below

So time taken by clicks to reach the bottom will be:

time = distance/speed of sound in water = d/V = 55/(1530)

time = 0.036 sec

Now we need time in which echoes of clicks will be heared by dolphin will be:

T = 2*t = 2*0.036 = 0.072 sec

Part B.

wavelength is given by:

= V/f

f = frequency of sound = 55 kHz = 55000 Hz

So,

= 1530/55000

= 0.0278 m = 27.8*10^-3 m = 27.8 mm = wavelength of sound

Let me know if you've any query.