A bat emits ultrasonic sound of frequency 100 kHz in air. If this sound meets a water surface, the wavelengths of the reflected and transmitted sound are (Speed of sound in air = 340 m `s^(-1)` and in water = 1500 m `s^(-1)` )

Options

A. `3.4mm,30mm`
B. 6.8 mm, 15 mm
C. 3.4 mm, 15 mm
D. 6.8 mm, 30 mm

Answer

C

Explanation

Here, `upsilon=100kHz=100xx10^(3)`Hz
`=10^(5)Hz=10^(5)s^(-1)`
`v_(a)=340ms^(-1),v_(w)=1500 ms^(-1)`
Frequency of both the reflected and transmitted sound remains unchanged.
Wavelength of reflected sound.
`lamda_(a)=(v_(a))/upsilon=(340 ms^(-1))/(10^(5)s^(-1))=34xx10^(-4)m`
`=3.4xx10^(-3)m=3.4 mm`
Wavelength of transmitted sound,
`lamda_(w)=(v_(w))/(upsilon)=(1500ms^(-1))/(10^(5)s^(-1))=15xx10^(-3)m=15 mm`