Waves in air, fluids and solids

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Question 17
Medium

An underwater research station uses two acoustic positioning beacons, Beacon X and Beacon Y, to transmit ultrasonic positioning pulses to a submerged robotic drone (ROV). Beacon X is situated closer to the ROV than Beacon Y, as illustrated in the schematic below.

Underwater acoustic positioning setup

An ultrasonic calibration pulse transmitted by the beacons has a frequency of 25.0 kHz25.0\text{ kHz}25.0 kHz.

a.

Convert this frequency into hertz (Hz\text{Hz}Hz).

[1]
b.

Calculate the period of this acoustic wave.

[2]
c.

Calculate the wavelength of an acoustic wave with a frequency of 37 500 Hz37\,500\text{ Hz}37500 Hz when the speed of sound in seawater is 1500 m/s1500\text{ m/s}1500 m/s. State the correct unit for wavelength.

[3]
d.

Write down the equation that links distance (sss), speed (vvv), and time (ttt).

[1]
e.

Calculate the time taken for the pulse to travel from Beacon X to the ROV over a distance of 75.0 m75.0\text{ m}75.0 m where the speed of sound in seawater is 1500 m/s1500\text{ m/s}1500 m/s.

[2]
f.

The acoustic pulses from both Beacon X and Beacon Y travel at the same speed of 1500 m/s1500\text{ m/s}1500 m/s. Explain why the pulse from Beacon Y must be transmitted slightly before the pulse from Beacon X for the ROV to receive them at the exact same instant.

[3]

Waves in air, fluids and solids Questions

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