A bat is flitting about in a cave, navigating via ultrasonic beeps. Assume that the sound emission frequency of the bat is 40kHz. During the fast swoop directly toward a flat wall surface, the bat is moving at 0.03 times the speed of sound in air. What frequency does the bat hear reflected off the wall?

Explanation

`f =40 kHz, v_(b) = 0.03 v`
Apparent frequency `f' = 40 ((v+0.03v)/( v- 0.03v)) kHz`
i.e., `f '= ( 40 xx ( 1.03))/(0.970 ) kHz`
i.e., `f' = 42.4 kHz`