1. Doppler Effect and Interference

2. Doppler Effect
The change in wave frequency due to a moving wave source or observer
4 cases can cause this effect:
1. Source moving toward observer
2. Source moving away from observer
3. Observer moving toward source
4. Observer moving away from source

3. Resting sound source Frequency fs V=340m/s Frequency fo source at rest
observer
at rest

4. Sound source moving toward observer
Observer hears
increased pitch
(shorter wave length)
Frequency fo
Frequency fs
source
observer
at rest

5. Sound source moving away from observer
Observer hears
decreased pitch
(longer wave length)
Frequency fo
Frequency fs
observer
at rest
source

6. Sound Source At Rest and Observer Moving
As the observer gets closer to the source the wavelengths decrease, increasing frequency and pitch.
As the observer moves away from the source the wavelengths increase and decreasing frequency pitch

7. Interference Is the ability of two or more waves to form a new wave.
- There are two types of interference
1. Destructive
2. Constructive

8. Destructive Interference
When the compression of one wave will arrive with the rarefaction of another wave and cancel each other out

9. Constructive Interference
When the compressions of different waves arrive at the same place at the same time
This ends up forming a greater compression