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Sounds to ring around.

Light of a single wavelength passing through a convex lens sitting on a glass plate produces a distinctive pattern of dark and bright rings centered at the point where lens and plate touch. Such a pattern, known as Newton's rings, results when light reflected from the plate interferes with light reflected from the lens surface. At certain viewing angles, the commingled light waves cancel each other, creating a dark ring. At other angles, they reinforce each other, producing a bright ring.

David K. Hsu and Vinay Dayal, engineers at Iowa State University in Ames, now report observing Newton's rings created by high-frequency sound waves. They first noted the presence of wavy light and dark contours in ultrasonic scans of two revited, adhesively bonded aluminum plates. Further tets revealed that the concentric rings observed around the tightened fasteners were caused by the interference of sound waves reflected from the two adjacent inner surfaces of the aluminum plates.

"The ability to interpret the interference fringes would help the quantitative evaluation of adhesively bonded aircraft structures," the researchers conclude in the March 9 APPLIED PHYSICS LETTERS.
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Title Annotation:sound waves create Newton's rings pattern
Publication:Science News
Date:Mar 21, 1992
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