Doppler Effect

A passenger sitting in a moving train $A$ records a frequency of $5.5 \mathrm{kHz}$ while the train approaches the siren. During his return journey in a different train $B$, he records a frequency of $6.0 \mathrm{kHz}$ while approaching the same siren. Given siren placed at a railway platform is emitting sound of frequency $5 \mathrm{kHz}$. Find the ratio of velocity of train $B$ to that of train $A$.

A bus is moving with a velocity of $5 \mathrm{m} {\mathrm{s}}^{-1}$ towards a huge wall. The driver sounds a horn of frequency $165 \mathrm{Hz}$. If the speed of sound in air is $335 \mathrm{m} {\mathrm{s}}^{-1}$, Calculate the number of beats heard per second by a passenger on the bus. Take speed of sound $=335 \mathrm{m} {\mathrm{s}}^{-1}$.

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 $340 \mathrm{m}/\mathrm{s}$)

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

A source on a swing which is covering an angle $\theta$ from the vertical is producing a frequency $v.$ The source is distant $d$ from the place of support of the swing. If 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 source of sound $S$ emitting waves of frequency $100 \mathrm{Hz}$ and an observor $O$ are located at some distance from each other. The source is moving with a speed of $19.4{ \mathrm{m} \mathrm{s}}^{-1}$ at an angle of $60°$ with the source observer line as shown in the figure. The observer is at rest. The apparent frequency observer by the observer (velocity of sound in air $330{ \mathrm{m} \mathrm{s}}^{-1}$) is:

Policemen buzz a whistle frequency $400 \mathrm{Hz}$. A car driver is approaching the policemen. The speed of a car is $72 \mathrm{km} {\mathrm{h}}^{-1}.$ Find out the change in frequency experienced by the driver when a driver approaches the policemen, and after he crosses the policemen? [Velocity of sound is$\left.350{ \mathrm{m} \mathrm{s}}^{-1}\right]$.

Assertion: Motion of source with respect to the stationary observer is not equivalent to the motion of an observer with respect to a stationary source.

Reason: Doppler formula for a sound waves is symmetric with respect to the speed of the source and speed of the observer.

Two sources are at a finite distance apart. They emit sounds of wavelength $\lambda$. An observer situated between them on the line joining approaches one source with speed $u$. Then the number of beats heard by observer will be :

When an engine passes near to a stationary observer then its apparent frequencies occurs in the ratio $\frac{5}{3}$. If the velocity of sound is $340 \mathrm{m} {\mathrm{s}}^{-1}$ then the speed of the engine is

Source and observer both start moving simultaneously from the origin, one along $X-$axis and the other along $Y-$axis with a speed of source equal to twice the speed of the observer. The graph between the apparent frequency $(n\text{'})$ observed by observer and time $t$ would be: ($n$ is the frequency of the source)

As the train crosses a stationary observer, the apparent change in frequency of sound is in the ratio $5 : 3.$ If the velocity of sound in air is $332 \mathrm{m} {\mathrm{s}}^{-1}$, the velocity of train is

A source and observer are approaching each other with $50{ \mathrm{m} \mathrm{s}}^{-1}$ velocity. What will be the original frequency if the observer receives $400$ cycles per second?

A source is approaching a stationary observer with velocity ${\left(\frac{1}{10}\right)}^{\text{th }}$ that of sound. The ratio of observed and real frequencies will be:

A small source of sound moves on a circle as shown in the figure and an observer is sitting at $O$. Let at ${\nu }_1, {\nu }_2, {\nu }_3$ be the frequencies heard when the source is at $A, B$, and $C$ respectively.

An observer starts moving with uniform acceleration, towards a stationary sound source of frequency$f_0$. As the observer approaches the source, the apparent frequency(f) heard by the observer varies with time ($t$) is

A sound wave of wavelength 90 cm in glass is refracted into air. If the velocity of sound in glass is $5400\mathrm{ }\mathrm{m}/\mathrm{s}\mathrm{e}\mathrm{c}$ , the wavelength of the wave in air is -

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

The driver of car travelling with speed 30 m/sec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is