A level Doppler Effect Quiz 1

16 Questions

Quiz Description

A level Doppler Effect Quiz. The Doppler effect (or the Doppler shift) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.

A common example of Doppler shift is the change of pitch heard when a vehicle sounding a horn approaches and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.

The reason for the Doppler effect is that when the source of the waves is moving towards the observer, each successive wave crest is emitted from a position closer to the observer than the crest of the previous wave. Therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrivals of successive wave crests at the observer is reduced, causing an increase in the frequency. While they are traveling, the distance between successive wave fronts is reduced, so the waves "bunch together". Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wave fronts is then increased, so the waves "spread out".

1:

A change in observed frequency of a wave when a source or detector moves relative to transmitting medium is


Correct
  • 1:
    Doppler effect
  • 2:
    Thermal Effect
  • 3:
    Newton's Effect
  • 4:
    Elastic Effect
2:

Which of the following best describes the effect of the Doppler shift on the appearance of stars moving towards Earth?


Correct
  • 1:
    They appear brighter
  • 2:
    They appear more red
  • 3:
    They appear smaller
  • 4:
    They appear more blue
3:

A sound source with a frequency of 790Hz moves away from a stationary observer at a rate of 15m/s. What frequency does the observer hear?


Correct
  • 1:
    757Hz
  • 2:
    826Hz
  • 3:
    655Hz
  • 4:
    775Hz
4:

A fire truck emits an 880Hz siren. As the truck approaches an obeserver on the sidewalk, he perceives the pitch to be 950Hz. Approximately what pitch does he hear after the truck passes and is moving away? Assume the truck's velocity remains constant, and that the velocity of sound in air is 340m/s.


Correct
  • 1:
    810Hz
  • 2:
    800Hz
  • 3:
    820Hz
  • 4:
    840Hz
5:

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of v=331m/s+0.6m/s(T), where T is the temperature in °C.

As a person walks towards the speaker, the frequency he or she hears __________.


Correct
  • 1:
    decreases
  • 2:
    increases or decreases, depending on temperature
  • 3:
    remains the same
  • 4:
    increases
6:

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of v=331m/s+0.6m/s(T), where T is the temperature in °C.

A person runs away from the speaker at 3m/s, while it creates a 200Hz sound wave. What frequency does he or she hear?

Use 340m/s for the speed of sound.


Correct
  • 1:
    198.2Hz
  • 2:
    220.9Hz
  • 3:
    190.7Hz
  • 4:
    201.3Hz
7:

The source of a sound moves away from the listener. The listener has the impression that the source is __________.


Correct
  • 1:
    lower in velocity
  • 2:
    lower in pitch
  • 3:
    higher in amplitude
  • 4:
    higher in tone
8:

You are jogging on the sidewalk at a rate of 3m/s. A police car behind you is patrolling at a rate of 4m/s when it turns on its siren. If the siren has a frequency of 10000Hz, is the frequency you perceive higher or lower than the frequency emitted?


Correct
  • 1:
    Neither higher nor lower because the doppler effect only affects sounds at lower frequencies
  • 2:
    Higher because the overall distance between you and the siren is decreasing
  • 3:
    Higher because the siren is traveling the same direction as you
  • 4:
    Lower because the overall distance between you and the siren is increasing
9:

A star emits visible color at 550nm. If the star is moving away from a stationary observer, which of the following cannot be the wavelength observed?


Correct
  • 1:
    552nm
  • 2:
    568nm
  • 3:
    530nm
  • 4:
    584nm
10:

Two cars approach each other at 50m/s when one car starts to beep its horn at a frequency of 475Hz. What is the wavelength of the horn as heard by the other driver?

Vsound=343m/s


Correct
  • 1:
    0.54m
  • 2:
    1.23m
  • 3:
    1.52m
  • 4:
    1.00m
11:

A fire truck emitting a siren at 1000Hz moves at 45m/s towards a jogger. The jogger is moving at 5m/s towards the fire truck. Take the speed of sound to be 345m/s.

At what frequency does the jogger perceive the siren?


Correct
  • 1:
    834Hz
  • 2:
    960Hz
  • 3:
    1166Hz
  • 4:
    1333Hz
12:

What sort of waves exhibit the Doppler effect?


Correct
  • 1:
    light waves.
  • 2:
    water waves.
  • 3:
    sound waves.
  • 4:
    all of the above.
13:

The Doppler effect is produced if


Correct
  • 1:
    the source is in motion.
  • 2:
    the detector is in motion
  • 3:
    both of the above.
  • 4:
    none of the above.
14:

A person carrying a whistle, emitting continuously a note of frequency 272Hz is running towards a reflecting surface with a speed of 18km/hour. The speed of sound in air is 345m/s. The number of beats heard by him per second is


Correct
  • 1:
    4
  • 2:
    6
  • 3:
    8
  • 4:
    3
15:

The apparent frequency of the whistle of an engine changes in the ratio 9:8 as the engine passes a stationary observer. If the velocity of the sound is 340ms-1, then the velocity of the engine is


Correct
  • 1:
    40 m/s
  • 2:
    20 m/s
  • 3:
    340 m/s
  • 4:
    320 m/s
16:

Two trains A and B approach a station from opposite sides, sounding their whistles. A stationary observer on the platform hears no beats. If the velocities of A and B are 15m/s and 30m/s respectively and the real frequency of the whistle of B is 600 Hz, the real frequency of the whistle of A is ( Velocity of sound = 330m/s)


Correct
  • 1:
    660 Hz
  • 2:
    630 Hz
  • 3:
    570 H/z
  • 4:
    600 Hz

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A level Doppler Effect Quiz 1
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