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?
(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.
(c) The loud sound is heard due to the constructive interference of the sound waves. State how the constructive interference occurs.