Two similar loudspeaker are placed 0.8 m apart. They emit a coherent sound wave. A girl walks slowly parallel to the two loudspeakers at a distance 3.2 m in front of the loudspeakers. She hears a loud sound and weak sound alternately. Figure 2.1 shows the positions of the loud and weak sounds.
(a) What is meant by a coherent wave?
[1]
(b) The distance between three positions of the loud sound is 4.5 m, as shown in Figure 2.1.
Calculate the wavelength of the sound wave.
[3]
(c) The loud sound is heard due to the constructive interference of the sound waves. State how the constructive interference occurs.
[1]
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