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Physics in Action
Sep 21, 2004
Phononic crystals bring sound to a focus
Three years ago researchers at the University of California at San Diego created a storm in the world of optics when they announced that they had made a material that exhibited negative refraction. Light rays entering such a "negative index" material are not bent towards the normal -- as happens in all known materials in nature -- but beyond the normal. Now physicists in China and Canada have demonstrated the equivalent phenomenon with sound waves in a material known as a "phononic crystal".