| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. Physics and Physical Oceanography Bibliography: leaves 77-78 A wave pulse can propagate with a negative group velocity when it travels through a medium with anomalous dispersion, that is, when the derivative of the dispersion curve is negative. Here we report on the experimental observation of negative group velocities for pulses of ultrasound propagating ballistically through water containing gas bubbles. For frequencies near the resonant frequency of the bubbles, the absorption increases strongly and the group velocity becomes negative. Our experimental results are in good agreement with a theoretical model sound propagation in bubbly liquids if we assume a Gaussian distribution of bubble sizes.
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