Target: 10 Questions in 10 minutes

Includes some SL questions

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

I. wavelength
II. wave speed
III. frequency
  • A. All three.
  • B. I and II
  • C. I and III
  • D. II and III

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 can be used - in certain circumstances - to calculate the doppler effect on the frequency of waves.

doppler effect formula

Which of the following best describes the use of this formula?

  • A. Used when the velocity of source/observer is much smaller than the wave speed
  • B. Can only be used for a moving observer, not a moving source.
  • C. Can only be used for a moving source, not a moving observer.
  • D. Can only be used if both source and observer are moving.

 

 

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

doppler formula options x4

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?

 

7-10. Waves of frequency 2.0 Hz are moving across a lake at 3 ms-1. A canoe is paddled across the lake towards the wave source at a speed of 1 ms-1.

 canoe on lake
Image by Pexels from Pixabay

7. From the canoe, what is the observed frequency of the waves?

  • A. 0.5 Hz
  • B. 1.5 Hz
  • C. 2.7 Hz
  • D. 3.0 Hz

8. How fast would the canoe be travelling so that the observed frequency is 3 Hz?

  • A. 1.5 ms-1
  • B. 2.5 ms-1
  • C. 4.5 ms-1
  • D. 6.0 ms-1

9. The canoe turns round and now moves away from the source, at the same speed of 1 ms-1. What is the new observed frequency of the waves?

  • A. 0.5 Hz
  • B. 1.3 Hz
  • C. 1.5 Hz
  • D. 2.0 Hz

10. How fast would the canoe be travelling away from the source so that the observed frequency is 1 Hz?

  • A. 1.5 ms-1
  • B. 2.5 ms-1
  • C. 4.5 ms-1
  • D. 6.0 ms-1