Transverse and Longitudinal Waves

Transverse Waves

横波

For transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple on a pond and a wave on a string are easily visualized transverse waves.

对于横波，介质的位移方向与波的传播方向垂直。水面的涟漪和弦上的波都是容易想象的横波。

Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

横波不能在气体或液体中传播，因为没有机制可以驱动波传播方向垂直的运动。

Sound Waves in Air

空气中的声波

A single-frequency sound wave traveling through air will cause a sinusoidal pressure variation in the air. The air motion which accompanies the passage of the sound wave will be back and forth in the direction of the propagation of the sound, a characteristic of longitudinal waves.

一个单频声波在空气中传播时，会在空气中引起正弦形式的压力变化。声波通过时伴随的空气运动将在声波传播的方向上往复运动，这是纵波的一个特征。

Physics professor Clint Sprott of the University of Wisconsin shows one way to visualize these longitudinal pressure waves in his "Wonders of Physics" demonstration show. A loudspeaker is driven by a tone generator to produce single frequency sounds in a pipe which is filled with natural gas (methane). A series of holes is drilled in the pipe to release a small amount of gas. Igniting the gas produces flames for which the height increases with the pressure in the pipe. The pattern of the flames shows the pressure variation and can be used to roughly measure the wavelength of the pressure wave in the pipe.

威斯康星大学的物理教授克利特·斯普罗特在他的‘物理奇观’演示节目中展示了一种可视化这些纵波的方法。一个扬声器由音发生器驱动，产生单一频率的声音，在一个充满天然气（甲烷）的管道中传播。管道上钻了一系列小孔以释放少量气体。点燃气体会产生火焰，火焰的高度随管道内的压力变化而变化。火焰的模式显示了压力变化，可以用来大致测量管道中压力波的波长。

Low frequency

低频

High frequency

高频

Shown below is more detail on the attachment of the loudspeaker to the pipe. The loudspeaker is driven by the amplified output of a tunable oscillator.

如下面所示，是扬声器与管道连接的更多细节。扬声器由可调振荡器的放大输出驱动。

A series of small holes were drilled at regular intervals in the pipe. They appeared to be about 8 mm apart.

在管道上定期钻了一系列小孔。它们看起来大约相隔8毫米。