doppler effect

• The wavelength of sound waves made by moving sources get squished and stretched. This changes their

  wavelength and frequency heard by someone standing still making them sound different
• moving source, moving towards stationary observer


  The sound waves are going to bunch up in front of the source. That’s because the source is moving into the sound waves it makes. -> wavelength squishes up and it gets smaller, So the frequency must go up (v = ƒλ)

  v is fixed and λ goes down so ƒ must go up.

  
• ƒ real frequency ƒ’ fake frequency

  
  

  as the source approaches the observer, ƒ’ > ƒ. The frequency goes up as the source approaches.
• observer frequency - source moving towards observer:

  ƒ’ = ƒ(vw/ vw - vs)
• when the source is driving off into the distance:

  ƒ’ < ƒ
• observer frequency - source moving away from observer:

  ƒ’= ƒ (vw/ vw+ vs)
• The Doppler Effect occurs when a sound source is moving relative to an observer.

  The wavelength either squishes up or stretches out.

  For approaching sources use the equation, for receding sources use the + equation
• Vw is the speed of the wave (e.g. speed of sound).

  Vs is the speed of the source (e.g. speed of a car).