Lesson 50: Doppler effect in sound and light

 

Aims

  • Experience the Doppler effect eeeeeeoowwwwwwwww.
  • Understand why the wavelength will be shorter when a wave source moves towards an observer.
  • Derive the equations for Doppler effect with source moving towards and away from observer.
  • Understand why the velocity of a wave will be greater when an observer moves towards the source.
  • Derive the equations  for the Doppler effect for observer moving towards and away from the source.
  • Solve problems involving the Doppler effect.
  • Understand why movement of the medium has no effect on the frequency.
  • See how a shock wave is created.
  • Use the equation for Doppler shift of light.
  

TOK

  • When talking about flying faster than the speed of sound you could mention Chuck Jeger and all those test pilots who risked (and some lost) their lives trying to advance technology.
 

Notes

Some students may not have noticed the Doppler effect so a video of an ambulance passing an observer is a good start.

Understanding why the wavelength changes due to the movement of the source is helped no end by showing an animation. to show how the usual static diagram is constructed. It is difficult to visualise that the outer ring was formed when the source was at the starting position. The derivation is quite easy once the diagram has been understood

Videos of planes breaking the sound barrier always go down well.

 

Test

Doppler effect

Doppler effect answers

Doppler mc test

Doppler problems

  

Text Book

Page 135 to 138

 

Homework

Problems 17 to 22

 

Vocabulary list

eeeeooowwww
Doppler
red shift
shock wave
sound barrier
 

SMART board Notes

  

 

 

Resources

  Car horn

This is a simple demonstration of the Doppler effect. if you have time you could go out on the road and do it for real however it might be difficult to explain as you drive past at 60 miles per hour.

  Sonic boom

I like this video clip especially the way you can see the plane getting tossed about in the slow motion sequence. Can't believe he was allowed to break the sound barrier so closed to that ship.

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