Question

A Train is moving uniformly with a velocity 'v' on a straight track
between two bridges A and B, the motion being towards A. An observer
on the train hears an echo of the trains whistle reflecting from each
of the bridge. If the velocity of the sound is 'v', Find the ratio of
wavelengths of the wave reflected from A and B and the ratio of the frequencies
of the echoes heard by the observer.