Waves and Oscillations

Doppler Effect

Why a passing siren changes pitch

  • High school
  • about 4 min
  • 4 of 5 in the family
Not started
ahead: 1.71×fbehind: 0.71×f

Parameters (c = wave speed)

f′=f \ raccc∓vzf' = f\,\ rac{c}{c \mp v_z}

• Ahead of the source the wavefronts bunch up -> higher frequency • Behind they stretch out -> lower frequency • That is why a passing siren changes pitch