Two loudspeakers driven in phase emit sound of frequency 680 Hz. At a point, the path difference from the two speakers is 0.75 m. What is heard there (speed of sound = 340 m/s)?
Correct answer D. A minimum, due to destructive interference
Explanation
λ = v/f = 340/680 = 0.50 m. The path difference 0.75 m equals 1.5λ, an odd number of half wavelengths, so the waves arrive in antiphase and interfere destructively.
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