The Doppler Effect

The Doppler Effect

1. Named after Austrian physicist Christian Doppler

   • Proposed it in 1842

2. Apparent change in frequency of an object

   • Appears higher when approaching
     • Appears lower when moving away

3. Examples

   • Siren from an ambulance
   • Sound from a passing race car

4. Object moving towards stationary observer

   • Apparent frequency - f'
     • f'=\(\frac{v}{v-vs}\)f

5. Object moving away from stationary observer

   • Apparent frequency - f'
     • f'=\(\frac{v}{v+vs}\)

6. v = speed of wave

   • vs = velocity of source
     • f = frequency of wave