When the observer moves towards the stationary source with velocity $V_1$,the apparent frequency of the emitted note is $F_1$. When the observer moves away from the source with velocity $V_1$,the apparent frequency is $F_2$. If $V$ is the velocity of sound in air and $\frac{F_1}{F_2}=2$,then $\frac{V}{V_1}=?$

An engine whistling at a constant frequency $n_0$ and moving with a constant velocity goes past a stationary observer. As the engine crosses him,the frequency of the sound heard by him changes by a factor $f$. The actual difference in the frequencies of the sound heard by him before and after the engine crosses him is

$A$ small source of sound moves on a circle as shown in the figure and an observer is standing at $O.$ Let $n_1, n_2$ and $n_3$ be the frequencies heard when the source is at $A, B$ and $C$ respectively. Then

$A$ source of sound $S$ is moving with a velocity of $50\,m/s$ towards a stationary observer. The observer measures the frequency of the sound as $1000\,Hz$. What will be the apparent frequency of the source when it is moving away from the observer after crossing him (in $,Hz$)? (Take the velocity of sound in air as $350\,m/s$)

$A$ police car with a siren of frequency $8 \ kHz$ is moving with uniform velocity $36 \ km/h$ towards a tall building which reflects the sound waves. The speed of sound in air is $320 \ m/s$. The frequency of the siren heard by the car driver is (in $kHz$)

This question has Statement $1$ and Statement $2$. Of the four choices given after the Statements,choose the one that best describes the two Statements.
Statement $1$: Bats emitting ultrasonic waves can detect the location of a prey by hearing the waves reflected from it.
Statement $2$: When the source and the detector are moving,the frequency of reflected waves is changed.