Question

A bat emits ultrasonic sound of frequency 1000 kHz in air. If the sound meets a water surface, what is the wavelength of (a) the reflected sound. (b) the transmitted sound? Speed of sound in air is $340m{s}^{-1}$ and in water $1486m{s}^{-1}$.

Answer 1

(a) Frequency of the ultrasonic sound, $f=1000kHz={10}^{6}Hz$
Speed of sound in air, $V_a=340m/s$
The wavelength $\left({\lambda }_r\right)$ of the reflected sound is given by the relation:

${\lambda }_r=V/f$
$=340/{10}^6=3.4\times {10}^{-4}m$.
(b) Frequency of the ultrasonic sound, $f=1000kHz={10}^{6}Hz$
Speed of sound in water, $V_w=1486m/s$
The wavelength of the transmitted sound is given as:

${\lambda }_r=1486/{10}^6=1.49\times {10}^{-3}m$.