$A$ sound wave of frequency $\nu$ travels horizontally to the right. It is reflected from a large vertical plane surface moving to the left with a speed $v$. The speed of sound in the medium is $c$. Then:

An observer is moving away from a source of sound of frequency $100 \, Hz$. His speed is $33 \, m/s$. If the speed of sound is $330 \, m/s$,then the observed frequency is .... $Hz$.

$A$ car moving towards a wall at a velocity of $30 \, m/s$ sounds a horn of frequency $600 \, Hz$. What frequency $(Hz)$ will the driver hear? (Speed of sound in air = $330 \, m/s$)

$A$ sound source,emitting sound of constant frequency,moves with a constant speed and crosses a stationary observer. The frequency $(n)$ of sound heard by the observer is plotted against time $(t)$. Which of the following graphs represents the correct variation?

$A$ train $S_1$,moving with a uniform velocity of $108 \ km/h$,approaches another train $S_2$ standing on a platform. An observer $O$ moves with a uniform velocity of $36 \ km/h$ towards $S_2$,as shown in the figure. Both the trains are blowing whistles of the same frequency $120 \ Hz$. When $O$ is $600 \ m$ away from $S_2$ and the distance between $S_1$ and $S_2$ is $800 \ m$,the number of beats heard by $O$ is: [Speed of sound $= 330 \ m/s$]

$A$ source at rest emits sound waves of frequency $102 \ Hz$. Two observers are moving away from the source of sound in opposite directions, each with a speed of $10 \%$ of the speed of sound. The ratio of the frequencies of sound heard by the observers is