A path is parallel to the line joining S, and S₂ and is 40.0 m from that line.

The sound from both loudspeakers now has a wavelength of 0.70 m.S₁ and S₂ now emit waves that are rad out of phase. The shortest distance along the path between a position with constructive interference and a position with destructive interference is x. Point Q is equidistant from S, and S₂. Which row gives x and the amplitude of the sound that is detected at Q?[

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