Answer:
0.25 m
Explanation:
v = Speed of sound in air at 20°C = 343 m/s
f = Frequency = 686 Hz
Wavelength is given by
[tex]\lambda=\dfrac{v}{f}\\\Rightarrow \lambda=\dfrac{343}{686}\\\Rightarrow \lambda=0.5\ m[/tex]
The wavelength is 0.5 m
Path difference for destructive interference
[tex]\Delta x=\dfrac{\lambda}{2}\\\Rightarrow \Delta x=\dfrac{0.5}{2}\\\Rightarrow \Delta x=0.25\ m[/tex]
The required distance is 0.25 m
