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DP IB Physics: HL

Topic Questions

Home / IB / Physics: HL / DP / Topic Questions / 9. Wave Phenomena (HL only) / 9.5 Doppler Effect / Multiple Choice


9.5 Doppler Effect

Question 1

Marks: 1

A stationary source emits sound wave with frequency f. An observer moving towards the source measures the sound as having frequency f space apostrophe. The speed of the observer is 20% of the speed of sound.

What is the the value of f space apostrophewhen the emitted frequency is 10 Hz?

  • 0.8 Hz

  • 1.2 Hz

  • 10.2 Hz

  • 12 Hz

Choose your answer
  
Key Concepts
The Doppler Equation

Question 2

Marks: 1

The flow of blood can be monitored using a machine which emits ultrasound of 10 MHz and is then able to measure the change in frequency when the pulse returns having reflected off a red blood cell.

When a wave is reflected from a moving object, the change in frequency is doubled compared to a situation where a sound is detected by a moving observer. Assume that the speed of sound in the body is the same as that of water, 1500 m s–1.

What is the frequency detected if blood is flowing away at 0.15 m s−1?

  • 10.002 MHz

  • 2000 Hz

  • 9.998 MHz

  • −2000 Hz

Choose your answer
  

Question 3

Marks: 1

A boat sits on a lake, and is hit by 4 waves every 10 s. As the boat starts to move in the same direction as the waves, exactly 2 waves from behind hit the boat every 10 s. The speed of the boat is 1.5 m s−1.

What is the speed of the waves?

  • 1.5 m s−1

  • 3 m s−1

  • 1500 m s−1

  • 340 m s−1

Choose your answer
  
Key Concepts
The Doppler Effect

Question 4

Marks: 1

A police car passes a stationary car at a speed of 30 m s−1. The police car is 2 m ahead of the car, and 2 m to the left as seen by the driver and emits a continuous tone of frequency 550 Hz.

Which of the following is an expression for the frequency of sound heard by the driver of the car, f space apostrophe?

  • 550 open parentheses fraction numerator 340 minus 15 square root of 2 over denominator 340 end fraction close parentheses

  • 550 open parentheses 340 over 370 close parentheses

  • 550 open parentheses 370 over 340 close parentheses

  • 550 open parentheses fraction numerator 340 over denominator 340 plus 15 square root of 2 end fraction close parentheses

Choose your answer
  
Key Concepts
The Doppler Effect

Question 5

Marks: 1

An alien living in another solar system sends a radio signal of frequency f to the next planet in their solar system. The signal reflects back and is recorded as having a frequency f space apostrophe which is lower than the original signal.

A few days later they repeat the experiment and find that the frequency change is less than that observed in the first experiment.

Which of the following could cause these effect?

  1. The atmosphere of the planet is rotating such that the radio beam reflects off a section that is moving away from the alien's planet 
  2. The planet is moving away from the alien's planet
  3. The atmosphere of the planet is rotating such that the radio beam reflects off a section that is moving towards the alien's planet 
  4. The planet is moving towards the alien's planet
  • I only

  • I and II

  • I and II, followed by II and III

  • Various combinations of I, II, III and IV

Choose your answer
  

Question 6

Marks: 1

In a binary star system, two stars orbiting each other can be observed using a spectrometer. The star system as a whole is moving away from the Earth at a constant velocity. The spectral lines appear to fluctuate. A graph can be plotted of relative velocity of each star compared to the observer.

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(a)
At which point on the graph will the stars be in the following position?
5irv5ae-9-5-ib-hl-mcqs-hard-q6-markscheme5irv5ae-9-5-ib-hl-mcqs-hard-q6-markscheme

    Choose your answer
      

    Question 7

    Marks: 1

    Photographs of lines in the spectrum of the Sun show changes in wavelength. The atmosphere of the sun rotates at a speed u subscript s, anti-clockwise as observed from its north pole.

    What is an expression for the observed change in wavelength lambda apostrophe of a spectral line from light emitted from the right hand edge of the Sun as viewed from the northern hemisphere on the Earth?

    Assume the Earth's orbit is circular.

    • lambda apostrophe equals lambda open parentheses 1 minus u subscript s over c close parentheses

    • lambda apostrophe equals lambda open parentheses 1 plus u subscript s over c close parentheses

    • lambda apostrophe equals lambda open parentheses 1 minus c over u subscript s close parentheses

    • lambda apostrophe equals lambda open parentheses u subscript s over c minus 1 close parentheses

    Choose your answer
      
    Key Concepts
    The Doppler Effect

    Question 8

    Marks: 1

    An asteroid which entered the Earth's atmosphere 64 million years ago emitted a sound of frequency 100 Hz due to the interaction with the atmosphere on its entry.

    A T. rex directly under the asteroid hears the noise, but hears it at a frequency of 200Hz. The distance from the top of the atmosphere to the ground is 102 km. 

    28yjpt61-9-5-ib-hl-mcqs-hard-q8-question

    How long does the T. rex have before the asteroid hits?

    • 10 minutes

    • 170 s

    • 170 mins

    • 6000 s

    Choose your answer
      

    Question 9

    Marks: 1

    The graph shows the dominant wavelength of light emitted by 4 different stars, and the same light observed from the Earth.

    brvkbczv-9-5-ib-hl-mcqs-hard-q9-question

    Which pair of stars are moving away from Earth at the same speed?

    • 1 and 2

    • 2 and 4

    • 3 and 4

    • 1 and 3

    Choose your answer
      

    Question 10

    Marks: 1

    A bat is flying towards a tree using echolocation to navigate. The bat emits an ultrasound pulse of 45 kHz. On reflection from the tree, the bat detects a frequency of 50 kHz. The bat is 170 m away from the tree. Due to reflection, the speed of the bat is halved because the Doppler effect is doubled.

    How long does the bat have to change course before hitting the tree?

    • 170 s

    • 10 s

    • 5 s

    • 1 s

    Choose your answer
      
    Key Concepts
    The Doppler Equation