A source of sound of frequency 256 Hz is moving towards a wall with a velocity of 5 m/s. How many beats per second will be heard by an observer O standing in such a positoin that the source S is between O and wall? `(c=330(m)/(s)`)

Explanation

Frequency of sound directly heard
`f_(1) = f_(0) ((v - v_(0))/(v - v_(s))) = 256 ((330)/(330 + 5))`
`= 252 . 2 Hz" ". . . (i)`
Frequency received by the wall
`f =f_(0) (v)/( v - v_(s)) = (256 xx 330)/(330 - 5 ) Hz " " . . . (ii)`
Frequency received by the observer directly `f_(2) = f ` (Because the wall is not moving)
thus , ` f_(2) = (256 xx 330)/(325) = 259 . 9 Hz `
Beats frequency ` = f_(2) - f_(1) = (259 .9 - 252 . 2 ) Hz = 7 . 7 Hz ` 7 beat per sound will be heard by the observer.