A train moving at a speed of $220$ $m{s}^{-1}$ towards a stationary object, emits a sound of frequency 1000 Hz. Some of the sound reaching the object gets reflected back to the train as an echo. The frequency of the echo as detected by the driver of the train is:(speed of sound in air is $330$ $m{s}^{-1}$)

1.  4000 Hz 

2.  5000 Hz 

3.  3000 Hz 

4.  3500 Hz

If a source moves perpendicularly to the listener, then the change in frequency will be:
1.  2n
2.  n
3.  n/2
4.  Zero

A car is moving towards a high cliff. The car driver sounds a horn at a frequency of 'f'. The reflected sound heard by the driver has a frequency of 2f. If 'v' is the velocity of sound, then the velocity of the car, in the same velocity units, will be:
1. v/3
2. v/4
3. v/2
4. v/$\sqrt{2}$

A whistle revolves in a circle with an angular speed ω = 20 rad/sec using a string of length 50 cm. If the frequency of sound from the whistle is 385 Hz, then what is the minimum frequency heard by an observer which is far away from the centre? (V_sound = 340 m/s)
1. 385 Hz
2. 374 Hz
3. 394 Hz
4. 333 Hz

An observer moves towards a stationary source of sound with a speed of 1/5th of the speed of sound. The wavelength and frequency of the source emitted are λ and f, respectively. The apparent frequency and wavelength recorded by the observer are, respectively:
1. 1.2f, 1.2λ
2. 1.2f, λ
3. f, 1.2λ
4. 0.8f, 0.8λ

A rocket is moving at a speed of \(200\) ms^–1 towards a stationary target. While moving, it emits a wave of frequency \(1000\) Hz. Some of the sound reaching the target gets reflected back to the rocket as an echo. The frequency of the sound as detected by the target and the frequency of the echo as detected by the rocket respectively are: (speed of sound = \(330\) m/s)
1. \(4080\) Hz and \(2540\) Hz
2.  \(1000\) Hz and \(1000\) Hz
3.  \(2540\) Hz and \(4080\) Hz
4.  \(2540\) Hz and \(2540\) Hz

The engine of a train sounds a whistle at frequency v. The frequency heard by a passenger is

1. > v

2. < v

3. \(=\frac{1}{v}\)

4. =v

The change in frequency due to Doppler effect does not depend on

1. the speed of the source

2. the speed of the observer

3. the frequency of the source

4. separation between the source and the observer

A small source of sound moves on a circle as shown in the figure and an observer is sitting at O. Let v₁, v₂, v₃ be the frequencies heard when the source is at A, B and C respectively.

1. v₁ > v₂ > v₃

2. v₁ = v₂ > v₃

3. v₂ > v₃ > v₁

4. v₁ > v₃ > v₂

A source of sound moves towards an observer.

1. The frequency of the source is increased

2. The velocity of sound in the medium is increased

3 The wavelength of sound in the medium towards the observer is decreased

4. The amplitude of vibration of the particles is increased