Three sources of sound S₁, S₂ and S₃ of equal intensity are placed in a straight line with S₁S₂ = S₂S₃ (figure 16-E5). At a point P, far away from the sources, the wave coming from S2 is 120^o ahead in phase of that from S¹. Also, the wave coming from S³ is 120^o ahead of that from S₂. What would be the resultant intensity of sound at P?

Two sources of sound, S₁ and S₂, emitting waves of equal wavelength 20.0 cm, are placed with a separation of 20.0 cm between them. A detector can be moved on a line parallel to S₁S₂ and at a distance of 20.0 cm from it. Initially, the detector is equidistant from the two sources. Assuming that the waves emitted by the sources are in phase, find the minimum distance through which the detector should be shifted to detect a minimum of sound.

Two speakers S₁ and S₂, driven by the same amplifier, are placed at y = 1.0 m and y = - 1.0 m (figure 16-E4). The speakers vibrate in phase at 600 Hz. A man stands at a point on the X-axis at a very large distance from the origin and starts moving parallel to the Y-axis. The speed of sound in air is 330 m/s. (a) At what angle θ will the intensity of sound drop to a minimum for the first time? (b) At what angle will he hear a maximum of sound intensity for the first time? (C) If he continues to walk along the line, how many more maxima can he hear?

Two coherent narrow slits emitting sound of wavelength λ in the same phase are placed parallel to each other at a small separation of 2λ. The sound is detected by moving a detector on the screen ∑ at a distance D(>>λ) from the slit S₁ as shown in figure (16-E6). Find the distance x such that the intensity at P is equal to the intensity at O.

Figure (16-E7) shows two coherent sources S₁ and S₂ which emit sound of wavelength λ in phase. The separation between the sources is 3λ. A circular wire of large radius is placed in such a way that S₁S₂ lies in its plane and the middle point of S₁S₂ is at the centre of the wire. Find the angular positions θ on the wire for which constructive takes place.