An ultrasound source and two ultrasound detectors are set up as shown. detector 1 source detector 2 The detectors are connected to an oscilloscope and photograph 1 shows the traces that are recorded. detector 1 trace detector 2 trace photograph 1 Detector 2 is moved slightly further away from the source and photograph 2 shows the traces that are recorded. detector 1 trace detector 2 trace photograph 2Detector 2 is moved back to its original position, alongside detector 1. Detector 2 is then steadily moved away from the source. This produces the traces seen in photograph 2 then photograph 1 alternately, until nine such cycles have been seen. The detector moves across a metre rule and the initial and final position of the detector are shown in photograph 3 and photograph 4. 10 in in m photograph 3 photograph 4 position position of detector of detector Calculate, using the results of this experiment, the speed of sound in air. frequency of ultrasound = 40.0 kHz