I have a question about Physics I would like to understand...

Question

Bats rely on sound localization to be able to fly during the night. On a cool 20 °C summer night, a bat produces an ultrasonic sound with a frequency of 39 kHz.

What is the wavelength of this ultrasound, in meters?

While remaining stationary, the bat emits a sound pulse and receives an echo after 0.150 sec. How far away, in meters, is the reflecting object from the bat?

Answer 1

Eunjin L.

20°C is close to room temperature and the speed of sound in air at room temperature is approximately 340ms^-1.

Using the wave equation v = f•λ, and substituting the values of speed and frequency, we get

λ = 340m/s÷39000Hz

= 0.0087m

Using the speed of sound as before, and substituting in the equation s=v•t

we get s = 340m/s•0.150s

= 51m.

Now the sound travels a total of 51m which means 51/2m up and 51/2m back so the object is 25.5m away.

I hope this helps. Mr. A