The sound from a single source can reach point O by two different paths. One path has a length 20.0 m and the second path has a length 21.0 m. The sound destructively interferes at point O. What is the minimum frequency of the source if the speed of sound is 340 m/s?
A)340 Hz
B)6800 Hz
C)520 Hz
D)680 Hz
E)170 Hz

Question

Quizplus · Accepted Answer

Destructive interference occurs when the path difference is an odd multiple of half wavelengths. The path difference here is 1.0 m. For the first minimum frequency, this path difference equals half a wavelength (λ/2). Therefore, λ = 2 m. Using the speed of sound (v = 340 m/s), frequency (f) is v/λ = 340/2 = 170 Hz.

The Sound from a Single Source Can Reach Point O