of the maximum intensity = ........ . Wn 5. Fig. 18 shows a loudspeaker placed in front of two narrow slits in a metal plate. The 1 10.40 m loudspeaker 5 m slits X Fig. 18 The loudspeaker emits sound waves of frequency 2.8 kHz. The separation between the art centres of the narrow slits is 0.40 m. A microphone, moved along the line XY at a distance of 5.0 m from the slits, detects regions of low and high intensity sound. The separation between adjacent regions of low and high intensity sound is 0.75 m. i. Explain how you can use an oscilloscope set to a time-base of 0.1 ms div-' to check that the frequency of sound is 2.8 kHz