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Question
A bat emits an ultrasonic sound of frequency 1000 kHz in the air. If the sound meets a water surface, what is the wavelength of the the reflected sound? The speed of sound in air is 340 m s–1 and in water 1486 m s–1.
Solution 1
Frequency of the ultrasonic sound, ν = 1000 kHz = 106 Hz
Speed of sound in air, va = 340 m/s
The wavelength (λr) of the reflected sound is given by the relation:
`lambda_r = v/v`
`= 340/10^6 = 3.4 xx 10^(-4)`
Solution 2
Here v = `1000 xx10^3` Hz = 10^6 Hz, `"v"_"a" = 340 "ms"^(-1)`
`"v"_"w" = 1486 "ms"^(-1)`
Wavelength of reflected sound, `lambda_"a"`
`= "v"_"a"/"v" = 340/ 10^6 "m"`
`= 3.4 xx 10^(-4) "m"`
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