A police siren emits a sinusoidal wave with frequency `f_(S) = 300 H_(z)` . The speed of the sound is `340 m//s`. (a) Find the wavelength of the waves if siren is at rest in the air . (b) If the siren is moving at `30 m//s`, Find the wavelength of the waves ahead of and behind the source.

Answer

A, B, C

Explanation

(a) `lambda = (nu)/(f) = (340)/(300) = 1.13 m` (b) Ahead
`f' = f ((nu)/(nu - nu_(s))) = 300 ((340)/(340 - 30))`
`= 329 H_(Z)`
`lambda' = (nu)/(f') = (340)/(329) = 1.03 m`
Behind
`f' = f ((nu)/(nu + nu_(s))) = 300 ((340)/(340 + 30))`
`= 275.67 H_(Z)`
`lambda' = (nu)/(f') = (340)/(275.67)`
`= 1.23 m`