Three sources of sound `S_(1),S_(2)` and `S_(3)` of equal intensity are placed in a straight line with `S_(1)S_(2) = S_(2)S_(3)` shown in the figure. At a point `P,` far away from the sources, the wave coming from `S_(2)` is `120^(@)` ahead in phase of that from `S_(1),` Also, the wave coming from `S_(3)` is `120^(@)` ahead of that from `S_(2).` What would be the resultant intensity of sound at `P` ?

Explanation

`S_(1):y_(1) = a sin omega t`
`S_(2):y_(2) = a sin (omega t + 120^(@))`
`S_(3):y_(3) = a sin (omega t + 240^(@))`
`y = y_(1) + y_(2) + y_(3) = A sin (omega t + theta)`

Resultant of these three amplitudes `= 0`