Δx = path difference between the waves from two speaker at the listener = difference in distance of speakers from the listener = 45 cm = 0.45 m
n = 1 (for fundamental frequency )
λ = wavelength
v = speed of sound = 340 m/s
f = frequency of the sound = ?
using the condition for constructive interference
Δx = n λ
0.45 = 1 λ
λ = 0.45 m
frequency of sound is given as
f = v/λ
f = 340/0.45
f = 756 Hz
nearest choice is 764 Hz , hence the correct choice is A. 764 Hz
