Q 17.4: Two speakers both emit sound of frequency 320 Hz, and are in phase. A receiver sits 2.3 m from one speaker, and 2.9 m from the other. What is the phase difference between the two sounds detected by the receiver

0.56*λ = 200º

Explanation:

In order to know the phase difference between the two sounds detected by the receiver, we need first to know the wavelength of the sound.Assuming that the sound wave is a plane wave, there exists a fixed relationship between the speed of sound, the frequency and the wavelength, as follows:

       

Assuming v= 343 m/s, and f = 320 Hz, we can find λ, as follows:

       

In order to know the phase difference, we need to know the path difference between both sounds, in units of wavelength:d = 2.9 m - 2.3 m = 0.6 mSo, we can the fraction of the wavelength represented by the distance d, as follows:

       

As a difference of 1 λ, means that both sounds arrive in phase each other, a difference of 0.56*λ, in degrees, is as follows:

       

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.