Every Source (speakers) generates sin waves. Following superposition principle,
a(t)=Asin(kx1−ωt)+Asin(kx2−ωt)=2Asin(k2x1+x2−ωt)cos(k2x1−x2) where k is wavenumber, k=λ2π,λ=80cm , a(t) is sound intensity function of time t, and x_1, x_2 - distances to speakers.
Therefore, the first minimum whould be
a(t)=0⇒cos(k2x1−x2)=0⇒k2x1−x2=2π
x1−x2=λ/2=40cm Obviously that x1+x2=L=2m, hence displacement
x=L/2−x1=λ/4=20cm Answer: (1) 20 cm
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