A bat emits ultrasound sound of frequency `100 kHz` in air. If this sound meets a water surface. What is wavelength of (a) the reflected sound wave (b) the trasmitted sound wave ?
Given speed of sound in air `= 340 m//s` and in water `= 1486 m//s`.

Answer

(a) `3.4 xx 10^-3 m` (b) `1.486 xx 10^-2 m`

Explanation

Here, `v = 100 kHz = 100 xx 10^3 Hz = 100000 Hz, v_("air") = 340 m//s, v_("water") = 1486 m//s`
(a) Wavelength of reflected wave `= ("speed of sound in air"(v_("air")))/(v) = (340)/(100000) = 3.4 xx 10^-3 m`
(b) Wavelength of transmitted wave through water `= ("speed of sound in water"(v_("water")))/(v)`
`=(1486)/(100000) = 1.486 xx 10^-2 m`.
(frequency of ultrasound does not change with change of medium).