DOPPLER'S EFFECT PHYS 101 LO5
Jul 15, 2015
DOPPLER'S EFFECTPHYS 101 LO5
Real Life Experience
• You must have noticed this before. As the train approaches the station, the sound of its horn at a higher pitch and as the train moved away, it is at a lower pitch.
Real Life Experience
• You must have noticed this before. As a train or a car approaches, the sound of its horn is at a higher pitch and as it moves away, the horn is at a lower pitch. (high pitch reflects high frequency)
This is Doppler's effect!!
Why does Doppler's effect occur?
• Click here for a passing car horn
You are here as the car approaches
↑
This is the car.
Why does Doppler's effect occur?
• Click here for a passing car horn
You are here as the car approaches
↑
This is the car.
Why does Doppler's effect occur?
This is the car.
You are here as the car leaves
Why does Doppler's effect occur?
• The Doppler effect occurs when a source of waves and the observer are moving relative to each other, resulting in the observer measuring a different frequency of the waves than the frequency that the source is emitting.
• The phenommenon is named for the Austrian physicist Christian Doppler (who first described it).
Three scenarios
• stationary source, moving receiver
• stationary receiver, moving source
• moving source and receiver
Three scenarios
• stationary source, moving receiver
• stationary receiver, moving source
• moving source and receiver
All can be concluded in one formula
• fr and fs: frequency of receiver and source
• vr and vs: speed of receiver and sourcer
• v: speed of sound in air
Questions
Assume you are Sitting on a beach one day. You find a flight is moving towords you with speed of 100m/s. What frequency will you hear as the plane flying towards you which engine emiting sound with a frequency of 1000 Hz?
solution
• What if the plane is leaving?
• What if the plane is leaving?
Resources
• http://www.physicsclassroom.com/class/sound/Lesson-3/The-Doppler-Effect-and-Shock-Waves