image credit: Jim Krider, Physics Instructional Resource Team, Arizona State University; larger image

Flame Tube

In the classic Ruben's tube demonstration, the tube containing the Bunsen burner gas has a speaker at each end that emits a pure tone. The tones have the same frequency and are in phase. The frequency of the tones is selected to set up a large standing wave inside the tube, and the resulting pressure distribution produces the pattern of flames. Read more on standing waves here.

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Light: The Physics of Art and Visual Perception

A diffracting grating shows the colors within light like a prism. The tiny slits that make up the grating bend entering light into different directions according to their wavelength, which shows the different colors.

In this activity you can look at the spectrum of light from a candle. Make sure to have adult supervision while working with flames. Diffracting gratings can be purchased cheaply online. Also, you can use your grating to investigate light produced by other light sources in your house.

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image credit: NASA; larger image

Not Just Another Old Flame

The photo shows two flames, one on Earth and one in space.

On Earth, the heat produced by the candle expands the nearby gas, and it makes the gas more buoyant, so it rises and produces the tall flame. Up in the Space Shuttle, it's quite different, since the Shuttle, the air inside, and the candle are in free fall; everything falls around Earth together, so there is no up or down created by gravity. In space, the flame spreads out equally in all directions, distributing the heat into a far larger volume than on Earth, and producing the cool blue flame.

To learn more, visit Not Just Another Old Flame.

Floating Flame Balls

In low gravity, fire behaves differently from our expectations, like in the image above. Read about the discovery of flame balls at Floating Flame Balls and more about the ongoing research in this Discover Magazine article.