Doppler Effect and Interference

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

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

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

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

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

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

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

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