An observer rides with a sound source of frequency `f` and moving with velocity `v` towards a large vertical wall. Considering the velocity of sound waves as `c`, find :
(i) The number of waves striking the surface of wall per second
(ii) The wavelength of the reflected wave
(iii) The frequency of reflected wave as observed by observer.
(iv) Beat frequency heard by the observer.

Answer

(i) `f' = (fc)/(c-v)`
(ii) `lambda' = lambda - ((v)/(f)) = ((c)/(f))-((v)/(f)) =((c-v)/(f))`
`f'' = f (c + v)/(c - v)`
(iv) `f_(beat) = f(2v)/(c - v)`