Section outline

  • Droplets create concentric circular waves in a body of water.

    No doubt you’ve seen this happen. Droplets of water fall into a body of water, and concentric circles spread out through the water around the droplets. The concentric circles are waves moving through the water.
    ::毫无疑问,你已经看到了这种情况。 水滴落到水中,而同心圆则在水滴周围的水中蔓延。 同心圆是波浪在水中流动。

    Waves in Matter
    ::物质波浪

    The waves in the picture above are examples of mechanical waves. A mechanical wave is a disturbance in matter that transfers through the matter. A mechanical wave starts when matter is disturbed. A source of energy is needed to disturb matter and start a mechanical wave.
    ::以上图象中的波是机械波的例子。 机械波是一种扰动, 它会通过物质转移。 当物质被扰动时, 机械波就会启动。 扰动物质和启动机械波需要能量源。

    Q: Where does the energy come from in the water wave pictured above?
    ::问题:上面所描绘的水浪中的能量来自何方?

    A: The energy comes from the falling droplets of water, which have because of their motion.
    ::A:能量来自滴落的水滴,由于水流的运动,水滴会下降。

    The Medium
    ::中 中

    The energy of a mechanical wave can travel only through matter. The matter through which the wave travels is called the medium ( plural , media). The medium in the water wave pictured above is water, a . But the medium of a mechanical wave can be any , even a .
    ::机械波的能量只能穿梭于物质中。波经过的事物被称为介质(多面、介质 ) 。 上面描绘的水波中的介质是水,一种。 但是机械波的介质可以是任何的,甚至是一个。

    Q: How do the particles of the medium move when a wave passes through them?
    ::问题:当波浪穿过时,介质的粒子如何移动?

    A: The particles of the medium just vibrate in place. As they vibrate, they pass the energy of the disturbance to the particles next to them, which pass the energy to the particles next to them, and so on. Particles of the medium don’t actually travel along with the wave. Only the energy of the wave travels through the medium.
    ::A: 介质的粒子只是振动而已。 当它们振动时,它们将扰动的能量传递到旁边的粒子上,它们把能量传递到旁边的粒子上,等等。 介质的粒子实际上不会随波而行。 只有波的能量通过介质。

    Types of Mechanical Waves
    ::机械波的类型

    There are three types of mechanical waves: transverse, longitudinal, and . They differ in how particles of the medium move. You can see this in the Figure .
    ::机械波有三种类型:反向、纵向和。它们与介质移动的粒子不同。您可以在图中看到这一点。

    Particle movement in transverse, longitudinal, and surface waves.

    • In a , particles of the medium vibrate up and down perpendicular to the direction of the wave.
      ::在 a 中, 介质振动的粒子向上和向下与波的方向垂直。
    • In a , particles of the medium vibrate back and forth parallel to the direction of the wave.
      ::在一个中位振动的粒子上 与波浪的方向平行
    • In a surface wave, particles of the medium vibrate both up and down and back and forth, so they end up moving in a circle.
      ::在一个表面波中, 介质的微粒向上、向下、向后和向后振动, 所以它们最终在一个圆形中移动。

    Q: How do you think surface waves are related to transverse and longitudinal waves?
    ::问题:你认为地表波与横向和纵向波有什么关系?

    A: A surface wave is combination of a transverse wave and a longitudinal wave.
    ::A:表面波是横向波和纵向波的组合。

    Summary
    ::摘要

    • A mechanical wave is a disturbance in matter that transfers energy through the matter.
      ::机械波是一种扰动 物质通过它转移能源。
    • The matter through which a mechanical wave travels is called the medium ( plural , media).
      ::机械波所穿行的事物称为介质(多元、媒体)。
    • There are three types of mechanical waves: transverse, longitudinal, and surface waves. They differ in how particles of the medium move when the energy of the wave passes through.
      ::机械波有三种类型:反向波、纵向波和表面波。当波的能量通过时,介质粒子的移动方式不同。

    Review
    ::回顾

    1. Define mechanical wave.
      ::定义机械波。
    2. What is the medium of a mechanical wave?
      ::机械波的介质是什么?
    3. List three types of mechanical waves.
      ::列出三种机械波。
    4. If you shake one end of a rope up and down, a wave passes through the rope. Which type of wave is it?
      ::如果你向上或向下摇一端的绳子,波会穿过绳子。是哪种波?