The wavelength is $120 \, cm$ when the source is stationary. If the source is moving with a relative velocity of $60 \, m/s$ towards the observer,then the wavelength of the sound wave reaching the observer will be ... $cm$ (velocity of sound $= 330 \, m/s$).

$A$ source of sound emits waves with frequency $f \, Hz$ and speed $V \, m/s$. Two observers move away from this source in opposite directions,each with a speed $0.2V$ relative to the source. The ratio of frequencies heard by the two observers will be

$A$ source of sound emits a sound wave of frequency '$f$' and moves towards an observer with a velocity $\frac{V}{3}$,where $V$ is the velocity of sound. If the observer moves away from the source with a velocity $\frac{V}{5}$,the apparent frequency heard by him will be:

An observer is standing $500 \,m$ away from a vertical hill. Starting between the observer and the hill, a police van sounding a siren of frequency $1000 \,Hz$ moves towards the hill with a uniform speed. If the frequency of the sound heard directly from the siren is $970 \,Hz$, the frequency of the sound heard after reflection from the hill (in $Hz$) is about, (velocity of sound $= 330 \,m/s$):

$A$ car is moving at a velocity of $17 \ m/s$ towards an approaching bus that blows a horn at a frequency of $640 \ Hz$ on a straight track. The frequency of this horn appears to be $680 \ Hz$ to the car driver. If the velocity of sound in air is $340 \ m/s$, then the velocity of the approaching bus is: (in $m/s$)

$A$ train approaching a railway crossing at a speed of $120 \ km/h$ sounds a whistle of frequency $576 \ Hz$,when it is $288 \ m$ away from the crossing. The frequency heard by an observer standing on the road perpendicular to the track at a distance of $384 \ m$ from the crossing is (Speed of sound in air $= 340 \ m/s$): (in $Hz$)