Each of two men A and B is carrying a source of sound of frequency n . If A approaches B with a velocity u
how many beats per second will be heard by B ? (Velocity of sound = c)

Explanation

Apparent frequency , n. ` (c + u_(0))/(c- u_(5)) xx n`
The distance between A and B is dacreasing . So , the velocity of the listener ` u_(0) ` and that of the source ` u_(s) ` , are both positive
When B is the listener, velocity of the listener, ` u_(0) =0 `,
Velocity of the source ` A , u_(s)= u `
So, ` n_(8) = (c) /(c-u) xxn `
Evidently, ` n_(8) gt n`
` therefore ` Number of beats per second
` therefore ` Number of beats per second
` n_(g) - n = ((c)/(c- u) -1)xx n = (u)/(c-u) n`