An engineer uses an ultrasonic flaw detector to inspect a steel railway axle. A short ultrasonic pulse is sent from one end of the axle along its length. A second pulse is received by the detector after a total time of 120μs. The speed of sound in steel may be taken as 5.0×103ms−1.
(i) Calculate the distance from the detector to the reflecting flaw inside the axle.
(ii) Explain briefly why two separate pulses (instead of one) are observed on the detector screen when a flaw is present.
(iii) State two advantages of using ultrasound rather than dismantling the axle for internal inspection.