Question

When I stand halfway between two speakers, with one on my left and one on my right, a musical note from the speakers gives me constructive interference. How far to my left should I move to obtain destructive interference?

a. one-fourth of a wavelength
b. half a wavelength
c. one wavelength
d. one and a half wavelengths
e. two wavelengths

Answer 1

Option B

Step-by-step explanation:

- Constructive interference occurs when two sound waves are coherent and their individual maximas coincide with each other when they meet. -

-Destructive interference occurs when the sound waves meet in-coherently. That is their maximas and minimas coincide leaving their net result to be either zero of very low.

- If scrutinize on a diagram of displacement against time of individual waves, we will see that Amplitudes of the two waves will will only destruct or reduce when positive part of one wave's cycle coincides with the negative part of the cycle of the other wave. Hence, we can see from a simple sketch that a phase shift of 1/2 a cycle of a wave is required that corresponds to 1/2 of wavelength. Hence option B is the correct answer.