Answer:
Explanation:
wavelength of sound = velocity / frequency
= 340 / 780
= .4359 m
Let the observer be at equal distance d from in phase source .
let it moves by distance x for destructive interference .
path difference from source
= d + x - (d - x )
= 2x
for destructive interference
path difference = wave length / 2
2x = .4359 / 2 m
x = .4359 / 4
= .108975 m
10.9 cm
so observer must move by distance 10.9 cm towards on of the centers.