µ IB | Doppler Effect

10 quick questions

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10 minutes maximum! (can you do it in 5?)

 

 

 1. The Doppler effect causes a shift in some properties of waves. Which quantities on the right are affected?

  • A. All three.
  • B. I and II
  • C. I and III
  • D. II and III

I wavelength

II wave speed

III frequency

2. An ambulance is moving towards an observer. Which of the following changes occurs to the sound wave heard by the observer?

frequency wavelength
A
stays the same increases
B
increases decreases
C
decreases stays the same
D
decreases decreases

 

3. 'Red shift' is an effect seen in distant galaxies. White light is shifted towards the red end of the spectrum. This is explained by...

  • A. the galaxy moving away from us, causing an increase in the wavelength.
  • B. the galaxy moving towards us, causing an increase in the wavelength.
  • C. the galaxy moving away from us, causing a decrease in the wavelength.
  • D. the galaxy moving towards us, causing a decrease in the wavelength.

 

4.The formula on the right is used to calculate the frequency recorded by an observer. Which of the following best describes the use of this formula?

  • A. Can be used for sound waves.
  • B. Can only be used for light waves.
  • C. Can only be used for a moving observer, not a moving source.
  • D. Can only be used if source and observer are moving closer together

 

 

5+6. These questions are about choosing the correct formula.
The following formulas can be used to find the frequency of an observed source:

Which of the above formulas should be use if we are trying to find the frequency...

 

5. .. heard when an observer is standing still, and a fire engine is approaching at high speed?

6. .. from a house fire alarm whilst the observer is moving away in a car?

 

7-9. A radio wave of wavelength 100 m is emitted from a distant galaxy, travelling away from us at 10% the speed of light.

 

7. The observed wavelength will be approximately:

  • A. 10 m
  • B. 90 m
  • C. 100 m
  • D. 110 m

8. The observed speed of light will be:

  • A. 0.1 c
  • B. 0.9 c
  • C. c
  • D. 1.1 c

9. The observed frequency will be approximately:

10. The doppler effect can be used to find...

  • A. the oxygen level in blood
  • B. an image of a foetus in the womb using ultrasound
  • C. the thickness of a thin film of glass or liquid
  • D. the speed of a vehicle using radar