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Speed of Sound Q?
An ultrasound unit sends a 3.20 MHz sound wave into a 28.8 cm long tube filled with an unknown liquid. A small microphone right next to the ultrasonic generator detects both the transmitted wave and the sound wave that has reflected off the far end of the tube. The two sound pulses are 5.00 divisions apart on an oscilloscope for which the horizontal time sweep is set to 62.0 µs/division. What is the speed of sound in the liquid?
The time between the pulses is how long it took the sound wave to travel to the end of the tube and back (so d=2L=2*(0.288m=0.576m).
The total travel time is 5 divisions * (62.0 µs/division) =310µs =3.1*10^-4 s
sound velocity = distance/time = 0.576m/(3.1*10^-4 s)=1858m/s
And that is a reasonable answer for a liquid that is more dense than water; for example, the speed of sound in room temperature water is 1493 m/s, but the speed of sound in glycerol is 1904m/s.
Hope that helps!
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