An engineer tests a steel plate for hidden internal cracks using an ultrasonic flaw detector. The speed of sound in steel is 5960 m/s.
(i) A pulse sent into the plate returns from the back surface after 80 µs. Calculate the thickness of the plate.
(ii) A second, earlier echo from a crack inside the plate is received 50 µs after the transmission of the pulse. Determine the distance of the crack from the front surface of the plate.
(iii) Give two advantages of using ultrasound rather than ordinary audible sound for detecting internal flaws in solids.
(iv) State any two similarities and one difference between the working principle of this flaw detector and that of a medical ultrasound scanner.