An ultrasonic transducer is being used to search for cracks within a thick concrete wall.  With the transducer in a given position, a pulse of ultrasound is sent out, and a reflected pulse is detected 40 microseconds later.  How deep beneath the surface of the wall is the crack from which the pulse reflected?  The speed of sound in concrete is 2000 m/s.0.04 m0.16 m0.08 m40 cm2Ultrasound is being used to examine an unborn baby.  If the baby’s head lies 4.5 cm beneath the surface of the mother’s skin, how long will it take a pulse of ultrasound to travel from a transducer at the surface to the baby’s head and back again?  The speed of ultrasound inside the body is roughly 1500 m/s.6 × 10-5 seconds3 × 10-5 seconds67.5 seconds135 seconds3A depth sounder is a device which allows a ship to measure the water depth at any point.  It works by using sonar to determine the distance to the river or sea bed or ocean floor.  A particular type of ship should not be taken into water which is less than 15 metres deep.  For this ship, what is the minimum safe time delay between sending a pulse of ultrasound vertically downwards and receiving the reflected pulse?  The speed of sound in water is approximately 1500 m/s.100 seconds0.02 seconds0.01 seconds50 seconds4Which one of the following statements about seismic waves is incorrect?S-waves are transverse wavesP-waves are longitudinal wavesS-waves can travel through both solid rock and liquid rockP-waves travel more quickly through solid rock than through liquid rock5A bat is using echolocation to locate its prey – an unfortunate fly!  The bat sends out a pulse of ultrasound and receives the pulse which was reflected from the fly 40 ms later.  How far is the fly from the bat?  Take the speed of sound in air to be 340 m/s.8.5 m6.8 m17 m13.6 m