- DOPPLER EFFECT:
Imagine that you are standing beside a railroad ttrack as a train approaches. The train blows its whistle.
Because of the train's motion, the sound waves of its whistle reach your ear a bit more rapidly than they would
if the train were stationary, so the whistle sounds higher in frequency or pitch.
After the train passes you and continues moving away, the sound waves of its whistle reach your ear more slowly than if
the train were stationary, so the whistle sound lower in frequency or pitch.
This phenomenon was first described by Christian Doppler (Austrian, 1800s), so it's called the Doppler effect.
- Application:
The same Doppler effect applies to all forms of wave energy--
- The frequency of any wave energy or radiation appears RAISED if the source of the radiation is moving toward us.
- The frequency of any wave energy or radiation appears LOWERED if the source of the radiation is moving away.
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