Flame Tube

Physics:	Sound, Waves
Grade Range:	Middle School, High School
Format:	Stage

This features our six foot Reuben's Tube, and is a very impressive demonstration on sound waves. this demonstration is a popular request, and is easily adapted to present to a variety of audiences.

Materials

• Flame Tube w/Hose
• Propane Tank
• Speaker w/Amplifier
• Tone Generator w/Cable
• Headphone Jack Cable
• Lighters (2)
• Optional: Slinkies
• Optional: Keyboard w/Cable Adapter
• Cellophane (for repairs)

Safety Precautions

Safety glasses must be worn at all times during this demonstration. The Flame Tube requires training on proper handling prior to use. This demonstration is sensitive to wind, so do not use outdoors or in a breezy room. Do not let the audience come any closer than six feet, and ask the audience to be quiet during the demonstration; it is sensitive to background noise.

Read the Fire Safety section of the Demonstration Safety Page before using this demonstration.

Demonstration

NOTE: When presenting this demonstration, you will need two tables to set up. Make sure to bring a power strip and extension cord!

Preparation: Set the Flame Tube on the first table, with both sets of feet rested on the same table. On a second table, set the speaker next to the Flame Tube, putting the speaker about 1/2 in away from the cellophane seal on the side of the tube, or as close as it can get without touching the tube. Next to the speaker, place the amplifier and tone generator. Connect the tone generator cable to the amplifier using the back port labeled "Phono". put the switch next to the port in the "phono" position. Make sure the main volume for the speaker is at zero, then plug in the amplifier and tone generator and turn them both on. Connect the propane tank to the flame tube, and before the start of the show open the propane tank fully. Attempt to ignite the holes on top of the propane tank once every minute, and once lit let it stand so the flames can grow.

Optional introduction

1. Ask the audience for examples of different types of waves. After hearing a few examples, State that there are three types of waves: Transverse, Longitudinal, and Surface Waves.
2. State that Transverse waves have an up-and-down motion. Ask the audience if they know how to do "the Wave", and have them do the wave back and forth across the room!
3. Pull out the slinky, and have your co-presenter hold one end as you hold the other. Working together, use the slinky to show a Transverse wave and a Longitudinal wave.
4. State that a Longitudinal wave is a Compression, and call up 4-5 volunteers. Have the volunteers stand in a line, with the speaker (you) on one end and the receiver (other presenter) on the other.
5. Turn and say "Hello" to the receiver. When you do, travel forward and bump into the first volunteer. Have the volunteers then travel down the line, bumping into each other until the last one bumps into the receiver. Explain how this shows a compression wave, with the "up" motion being two volunteers bumping into each other, and the "down" when they are separated.
6. State that a Surface wave is a combination of these two waves. Give examples of surface waves, like an ocean wave (water presses together, which creates the up-and-down motion we see) and seismic waves, or how earthquakes travel.

Flame Tube

1. Explain briefly the setup you are using; A speaker system is set against the Flame Tube, and by turning on the speaker you will put a sound wave through the tube, which we will see as a Transverse wave because of it compressing the propane inside the tube.
2. Set the tone generator to 210Hz, and turn up the speaker volume to 1/2 full. The flames will move, creating the wave!
3. Turn down the speaker volume, and explain the parts of the wave. State that the amplitude, or height of the wave, is adjusted by making the sound louder or quieter. Show this by turning the speaker up to 3/4 full, then off again.
4. Ask the audience what will happen if you were to double the frequency. If a younger audience, ask them if they should see more waves or less waves if the note became a higher pitch. Set the tone generator to 420Hz and turn the volume up 1/2 full. The number of waves doubles!
5. Flip the switch on the back of the amplifier to "Aux". Connect your phone or music player, and select a song to play for them! Songs that work well are:
   1. Secrets (OneRepublic)
   2. Let it Go (from Frozen)
   3. Photograph (Ed Sheeran)
   4. Fly Me to the Moon (Frank Sinatra)
   5. Iron Man (Black Sabbath)
   6. Stay the Night (Zedd, Haley Williams)
   7. Bangarang (Skrillex)

• NOTE: Use the two lighters to keep re-igniting the propane while you have a song playing. The music will put out flames as it plays. Only play 30-45 seconds of any one song, so that you can play a few different songs.
• When you finish presenting the Flame Tube, turn off the propane tank and detach it. Place the speaker on its side, and prop the flame tube on it, with a set of feet resting on the speaker. Ignite the propane coming out of the lower end of the tube, and let it burn off until it is time to pack up.

Why It Works

Short Explanation

This demonstration introduces Waves. There are three types of waves:

1. Transverse, or Sinusoidal waves. These are the up-and-down motion waves that we think of when we talk about waves. this is the way that electromagnetic waves travel, such as light and radio waves, which can travel through empty space!
2. Longitudinal, or Compression waves. These are the in-and-out waves that sound uses. This is the way sound waves travel, along with seismic waves, and works the best in liquids or solids!
3. Surface waves. These are a combination of the two types of waves stated above. Waves in water are a type of surface wave, since the up-and-down motion we see is caused by the water below the surface moving in-and-out!

Waves can be described by their different parts. When we look at the transverse wave we made with the flame tube, we can see that there are high points and low points. The Peak is the high point, and the Trough is the low point. the middle of the wave is called the Node, and the distance from one peak to the next is the Wavelength. The height of a wave is the Amplitude, which is often shortened to amp. To make a wave taller, you increase the volume, or amps. The make a wave shorter or longer, you have to adjust the Frequency, or the note. If you start at a note on a music scale (like Center C) and go up an octave (To High C), you are doubling the frequency of that note. Frequency and wavelength are inverse to each other, so when you double the frequency you cut the wavelength in half! Likewise, if you cut the frequency in half, you would double the wavelength.

When we listen to music, we know that there are a lot of notes in the music working together or against each other. By playing a song through the Flame Tube, you can see how some notes work together, creating really high flames or easy-to-see waves. You can also see where the notes don't work together, when certain spots in the flame tube get really low flames, or get put out!

Full Explanation

COMING SOON

Tips and Tricks

- Try to avoid using the Flame Tube at the end of a show, and to not run the Flame Tube for any more than 25 minutes at a time. This is to minimize any fire hazard, and to allow time so the flame tube can empty after a presentation.