Mission SM1 The Nature of a Sound Wave
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| Definition of Longitudinal Waves and Transverse Waves: There are a variety of wave types that can exist in a medium. The two most common types are longitudinal and transverse. A transverse wave is a type of wave in which particles of the medium vibrate in a direction that is perpendicular to the direction that the wave moves. |
As a sound wave moves from a source (say a tuning fork) to an observer, particles of the medium vibrate about a fixed position. The vibrations are in a back-and-forth direction aligned parallel to the line connecting the source and the observer.
One way of representing a sound wave is by means of a pressure plot. The vibration of particles of the medium about a fixed position results in regions of high pressure (compressions) and low pressure(rarefactions) in the space surrounding the source. These compressions and rarefactions are regularly spaced and travel from the source to the observer. The arrival of these regions at the observer's location (or any location) results in fluctuations of pressure with respect to time at that location. If a plot of pressure versus time at any location were constructed for a traveling sound wave, then the plot would show a sinusoidal variation in pressure with respect to time. The sinusoidal nature of the the graph might lead a student to believe that sound is a transverse wave. But don't be fooled! Sound is not a transverse wave since particles of the medium do not vibrate back and forth in a direction perpendicular to the direction that the sound wave moves.
