A sound source S is moving along a straight track with speed v, and is emitting sound of frequency ν_o (see figure). An observer is standing at a…

A sound source $\displaystyle S$ is moving along a straight track with speed $\displaystyle v$, and is emitting sound of frequency $\displaystyle \nu_{\mathrm{o}}$ (see figure). An observer is standing at a finite distance, at the point O, from the track. The time variation of frequency heard by the observer is best represented by : ( $\displaystyle \mathrm{t}_0$ represents the instant when the distance between the source and observer is minimum)