======Rubens Tube======


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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:** Standing Wave Flame Tube
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====Summary====                   
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====Procedure====  
  - Place the Rubens tube securely on stands with its mounts.  
  - Connect the propane tank to the tube using the hose and fitting.  
  - Position the speaker so it aligns with the silicone membrane at one end of the tube without touching it.  
  - Attach the speaker to an amplifier or function generator using cables.  
  - Open the propane valve and allow gas to flow into the tube.  
  - Light the holes along the tube to create a row of flames, adjusting height with the valve.  
  - Turn on the frequency generator and gradually change the frequency.  
  - Observe how the flames rise and fall in patterns that match the standing waves inside the tube.



====Links==== 
Ruben's Tube - Jared Ficklin: 
{{youtube>HpovwbPGEoo?}}\\

Ruben's Tube Theory - Outreach, Chem Eng, Univ of Utah: 
{{youtube>BbPgy4sHYTw?}}\\

📄 Rubens Tube - UCSC Physics Demonstration Room: [[https://ucscphysicsdemo.sites.ucsc.edu/physics-5b6b-demos/rubens-tube/]]\\

====Variations====
  * Use different sound sources (music, voice, or sine waves) to compare flame patterns.  
  * Test tubes of different lengths or diameters to explore changes in resonance.  
  * Replace propane with another safe gas to see how flame patterns differ.  
  * Use slow-motion video to capture the movement of the flames in detail.



====Safety Precautions====
  * Only operate in a well-ventilated area to avoid gas buildup.  
  * Always have a fire extinguisher and fire blanket nearby.  
  * Wear a fire-resistant lab coat and safety goggles.  
  * Ensure the tube is securely mounted before lighting.  
  * Never allow flames near the propane tank or hoses.  
  * Turn off gas supply immediately after the demonstration.




====Questions to Consider====
  * Why do the flames rise higher at some points and lower at others? (They follow the pressure variations of the standing wave, with more gas escaping at antinodes.)  
  * Why are only odd harmonics observed in the tube? (Because it acts as a closed-end tube with a displacement node at one end and an antinode at the other.)  
  * How could the speed of sound in propane be determined using this setup? (By measuring flame spacing for a known frequency and applying the wave equation.)  
  * What would change if the tube were open at both ends? (Even harmonics would also appear, altering the standing wave patterns.)