EQUINOX GRAPHICS / SCIENCE PHOTO LIBRARY EQUINOX GRAPHICS / SCIENCE PHOTO LIBRARY
Animation showing the passage of a sound wave through a gas. Sound is a compression wave, in which particles are first pushed forward then return to their original positions as the wave passes. This means there is a band of high density followed by a band of low density substance. The speed of sound is a function of the substance's compressibility, that is, how much it deforms under pressure. The greater the compressibility, the slower the passage of the wave. Gases are easiest to compress, followed by liquids and solids, and the speed of sound is therefore much faster in solids than in liquids, and faster in liquids than in solids. For instance, in air at sea level, the speed of sound is around 340 metres per second. In water, it is just less than 1500 metres per second, and in iron it is 5120 metres per second. See clips K002 8525 and K002 8526 for the wave in liquid and solid respectively, or K002 8523 for all three cases.
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