A water-level sensor is fixed to the bottom of a rainwater storage tank.
The sensor sends a pulse of ultrasound vertically upwards through the water. The pulse reflects from the water surface and returns to the sensor.
The pulse returns after 0.0040 s.
The speed of ultrasound in the water is 1500 m/s.
Calculate the total distance travelled by the pulse between being emitted and detected.
Calculate the depth of water above the sensor.
The ultrasound in the tank has a wavelength of 0.060 m.
Calculate the frequency of the ultrasound.
State why sound with the frequency you calculated in (c) is described as ultrasound.