Rubens' Tube

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A Rubens' Tube setup

The Rubens' tube, also known as the Standing wave flame tube, or simply flame tube, is a physics experiment demonstrating a standing wave. It shows the relationship between sound waves and air pressure.


[edit] Overview

A length of pipe is perforated along the top and sealed at both ends - one seal is attached to a small speaker or frequency generator, the other to a supply of a flammable gas (propane tank). The pipe is filled with the gas, and the gas leaking from the perforations is lit. If a constant frequency is used, a standing wave can form within the tube. When the speaker is turned on, the standing wave will create higher and lower pressure points along the tube. Where there is higher pressure due to the sound waves, more gas will escape from the perforations in the tube, and the flames will be higher at those points. In these cases, it is possible to determine the wavelength by simply measuring with a ruler.

[edit] History

John Le Conte discovered in 1858 that flames were sensitive to sound. In 1862 Rudolph Koenig showed that the height of a flame could be affected by transmitting sound in the gas supply, and the change as time passes could be displayed with rotating mirrors. August Kundt, in 1866, demonstrated an acoustical standing wave by placing seeds of lycopodium or cork dust in a tube. When a sound was made in the tube, the material inside lined up in nodes and antinodes in line with the oscillation of the wave, creating a standing wave. Later that century, Behn showed that small flames could be used as sensitive indicators of pressure. Finally, in 1904, using these two important discoveries, Heinrich Rubens, whom this experiment is named after, took a 4-metre-long tube and drilled 200 small holes into it at 2 centimeter intervals, and filled it with a flammable gas. After lighting the gas (whose flames all rose to near-equal heights), he noted that a sound produced at one end of the tube would create a standing wave, equivalent to the wavelength of the sound being made.[1].[2][3][4][5] O. Krigar-Menzel assisted Rubens with the theory.

Measuring the wavelength of a tone played into the device.

[edit] Public displays

A Rubens' Tube was on display at The Exploratory in Bristol, England until it closed in 1999, at which time the exhibit was moved to the @-Bristol museum.[6]
This display is also found in Physics departments at a number of Universities.[7]

[edit] References

  1. ^ Verhandlungen der Deutschen Physikalischen Gesellschaft, Nr.24 (30 Dec 1904) pp. 351, 352, 353, 354 "Stehende Schallwellen durch Manometerflammen, (Demonstrated by Heinrich Rubens, December, 8th 1904 )" via instructables
  2. ^ Annalen der Physik, vol. 322, Issue 6, pp.149-164 Flammenröhre für akustische Beobachtungen , H. Rubens, O. Krigar-Menzel (1905)
  3. ^ Philosophical Transactions of the Royal Society of London. "Series A, Containing Papers of a Mathematical or Physical Character", Vol. 230, pp. 413-445 (1932)
  4. ^ "The Flame Tube - ENGLISH TRANSLATION". Retrieved on November 8. 
  5. ^ "Luehrs Waterwave Englisch (.doc format)". Retrieved on November 8. 
  6. ^ "The Exploratory - Exhibits". Retrieved on November 6. 
  7. ^ "Oscillation & Waves". Retrieved on November 8. 

[edit] External links

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