$A$ source with a frequency of $500 \,Hz$ moves towards a stationary observer with a velocity of $30 \,m/s$. What frequency (in $Hz$) will the observer hear? (The speed of sound in air is $330 \,m/s$.)

Obtain the equation of frequency observed by a moving observer and a stationary source.

$A$ train moves towards a stationary observer with a speed of $34 \, m/s$. The train sounds a whistle and its frequency registered by the observer is $f_1$. If the speed of the train is reduced to $17 \, m/s$,the frequency registered is $f_2$. If the speed of sound is $340 \, m/s$,then the ratio $\frac{f_1}{f_2}$ is ..........

The driver of a car travelling with a speed $V_1 \ m/s$ towards a wall sounds a siren of frequency $n \ Hz$. If the velocity of sound in air is $V \ m/s$,then the frequency of sound reflected from the wall and as heard by the driver,in $Hz$,is

$A$ train standing at the outer signal of a railway station blows a whistle of frequency $400\, Hz$ in still air. What is the frequency of the whistle for a platform observer when the train recedes from the platform with a speed of $10\, m/s$? (Speed of sound $= 340\, m/s$)

$A$ source and an observer approach each other with the same velocity $50 \, m/s$. If the apparent frequency is $435 \, s^{-1}$,then the real frequency is .... $s^{-1}$ (Take speed of sound $v = 332 \, m/s$)