======Doppler Effect with a Tuning Fork======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Categories:** {{$demo.categories}}
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**Alternative titles:** Rotating Tuning Fork Doppler Effect
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====Summary====                   
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====Procedure====  
  - Tie a strong string securely to the handle of the tuning fork.
  - Strike the tuning fork gently with a mallet to start it vibrating.
  - Hold the free end of the string and begin rotating the tuning fork in a vertical or horizontal circle.
  - Listen carefully to the sound as the tuning fork moves toward you and then away from you.
  - Observe the change in pitch during different parts of the rotation.



====Links==== 
Doppler Effect (tuning fork) - WFU Physics Lecture Demonstrations: 
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Doppler Effect with Tuning Fork - Tony Verheyden: 
{{youtube>qD3UOS5BPGs?}}\\

📄 Doppler Turning Forks - Harvard Natural Sciences Lecture Demonstrations: [[https://old.physics.wfu.edu/demolabs/demos/3/3b/3B4018.html]]\\

📄 Doppler Turning Forks - Harvard Natural Sciences Lecture Demonstrations: [[https://sciencedemonstrations.fas.harvard.edu/presentations/doppler-tuning-forks]]\\


====Variations====
  * Change the speed of rotation to increase or decrease the size of the pitch change.
  * Use tuning forks of different frequencies to compare the effect.



====Safety Precautions====
  * Ensure the string is securely attached to prevent the tuning fork from flying off.
  * Keep a clear area around the demonstrator during rotation.
  * Do not rotate the tuning fork near faces or fragile objects.
  * Strike the tuning fork gently to avoid damage.




====Questions to Consider====
  * Why does the pitch increase as the tuning fork moves toward you? (The sound waves are compressed, increasing the observed frequency.)
  * Why does the pitch decrease as the tuning fork moves away? (The sound waves are stretched out, lowering the observed frequency.)
  * Does the tuning fork itself change frequency while rotating? (No, only the observed frequency changes.)
  * How is this demonstration similar to the sound of a passing siren? (Both involve a moving sound source creating a Doppler shift.)