Doppler Effect (in Sound)

A warship is fitted with SONAR operating at a frequency of $42 \mathrm{kHz}$. A submarine is approaching the ship with a speed of $72 \mathrm{km} {\mathrm{hr}}^{-1}$. If the speed of sound is $1400 \mathrm{m} {\mathrm{s}}^{-1}$, what will be the frequency of the sound received after being reflected from the submarine?

A source and an observer are situated on two perpendicular tracks as shown in the figure. The observer is at rest and the source is moving with a speed of $50 \mathrm{m} {\mathrm{s}}^{-1}$. The source emits a sound wave of frequency $75 \mathrm{Hz}$ which travel in the medium with a velocity of $200 \mathrm{m} {\mathrm{s}}^{-1}$. The frequency (in $\mathrm{Hz}$) of the sound heard by the observer when the source crosses the origin is,

A police man on duty detects a drop of $15\%$ in the pitch of the horn of a motor car as it crosses him. If the velocity of sound is $330 \mathrm{m} {\mathrm{s}}^{-1},$ calculate the speed of the car

A person carrying a whistle emitting continuously a note of $272 \mathrm{Hz}$ is running towards a reflecting surface with a speed of $18 \mathrm{km} {\mathrm{h}}^{-1}$. The speed of sound in air is $345 \mathrm{m} {\mathrm{s}}^{-1}$. The number of beats heard by him is:-

The frequency of a radar is $780 \mathrm{MHz}$. The frequency of the reflected wave from an aeroplane is increased by $2.6 \mathrm{kHz}$. The velocity of the aeroplane in $\mathrm{m} {\mathrm{s}}^{-1}$ is:

Two cars moving in opposite directions approach each other with the speed of $22 \mathrm{m} {\mathrm{s}}^{-1}$ and $16.5 \mathrm{m} {\mathrm{s}}^{-1}$ respectively. The driver of the first car blows a horn having a frequency $400 \mathrm{Hz}$. The frequency heard by the driver of the second car is [velocity of sound $340 \mathrm{m} {\mathrm{s}}^{-1}]$ (in $\mathrm{Hz}$ ):- ( Approximate the answer to nearest integer)

Two cars moving in opposite directions approach each other with speed of $22 \mathrm{m} {\mathrm{s}}^{-1}$ and $16.5 \mathrm{m} {\mathrm{s}}^{-1}$ respectively. The driver of the first car blows a horn having a frequency $400 \mathrm{Hz}$. The frequency heard by the driver of the second car is [velocity of sound $340 \mathrm{m} {\mathrm{s}}^{-1}$]:

A source on a swing that is covering an angle $\mathrm{\theta }$ from the vertical is producing a frequency $v$. The source is distant $d$ from the place of support of swing. If the velocity of sound is $c$, acceleration due to gravity is $g$, then the maximum and minimum frequency heard by a listener in front of swing is

A boy is walking away from a stationary wall at a speed of $1 \mathrm{m}/\mathrm{s}$ and blows a whistle whose frequency is $680 \mathrm{Hz}$. The number of beats heard by the boy per second is (Velocity of sound in air$=340 \mathrm{m}/\mathrm{s}$)

Two tuning forks $A$ and $B$ lying on opposite sides of observer $O$ and of natural frequency $85 \mathrm{Hz}$ move with velocity $10 \mathrm{m}/\mathrm{s}$ relative to a stationary observer $O$. Fork $A$ moves away from the observer while the fork $B$ moves towards him. Wind with a speed $10 \mathrm{m}/\mathrm{s}$ is blowing in the direction of motion of fork $A$. Find the beat frequency measured by the observer in $\mathrm{Hz}$. (Take speed of sound in air as $340 \mathrm{m}/\mathrm{s}$)

A source and a detector both start moving simultaneously from the position shown in the figure, one along $x$-axis and the other along $y$-axis with speeds $40 \mathrm{m} {\mathrm{s}}^{-1}$ and $30 \mathrm{m} {\mathrm{s}}^{-1}$ respectively. If $n$ is the frequency of the source then the graph between the apparent frequency $n\text{'}$ observed by detector and time $t$ would be [assume that source and detector do not collide]

A source and an observer are situated on two perpendicular tracks as shown in the figure. The observer is at rest and the source is moving with a speed of $50 \mathrm{m} {\mathrm{s}}^{-1}$. The source emits a sound wave of frequency $75 \mathrm{Hz}$, which travel in the medium with a velocity of $200 \mathrm{m} {\mathrm{s}}^{-1}$. The frequency of the sound heard by the observer when the source crosses the origin