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