Section outline

  • Lesson Objectives
    ::经验教训目标

    • Describe how waves move through water.
      ::描述波浪如何在水中移动。

    Lesson Vocabulary
    ::词汇表课程

    • wave
      ::电波


      ::电波

    Introduction
    ::导言

    If you've ever visited an ocean shore, then you know that ocean water is always moving. Waves ripple through the water, as shown in  Figure   . The water slowly rises and falls because of tides. You may see signs warning of currents that flow close to shore. What causes all these ocean motions? Different types of motions have different causes.
    ::如果你去过海边,那么你就会知道海洋水总是在移动。海浪在水中波及,如图所示。水因潮汐而缓慢上升和下降。你可能看到海流向岸边流动的迹象。是什么原因导致这些海洋运动?不同类型的运动有不同的原因。

    lesson content

     

    Waves cause the rippled surface of the ocean.
    ::海浪导致海洋的波纹表面

    Waves
    ::波浪

    Most ocean waves are caused by winds. A  wave  is the transfer of energy through matter. A wave that travels across miles of ocean is traveling energy, not water. Ocean waves transfer energy from wind through water. The energy of a wave may travel for thousands of miles. The water itself moves very little.  Figure    shows how water molecules move when a wave goes by.
    ::大多数海洋波都是由风造成的。波浪是能量通过物质转移。横跨海洋数英里的波浪是能量流动,而不是水流动。海浪的能量从风向水转移。波浪的能量可能行走数千英里。水本身移动很少。图显示当波浪经过时水分子是如何移动的。

    Anatomy of a wave

     

    A wave travels through the water. How would you describe the movement of water molecules as a wave passes through?
    ::一波穿过水面,你会如何描述水分子的移动?

    The Size of Waves
    ::波浪的大小

    Figure    also shows how the size of waves is measured. The highest point of a wave is the crest. The lowest point is the trough. The vertical distance between a crest and a trough is the height of the wave. Wave height is also called amplitude. The horizontal distance between two crests is the wavelength. Both amplitude and wavelength are measures of wave size.
    ::图中还显示了如何测量波的大小。波的最高点是峰顶。最低点是底部。顶部和底部之间的垂直距离是波的高度。波的高度也称为振幅。两个顶部之间的水平距离是波长。振幅和波长都是波的量度。

    The size of an ocean wave depends on how fast, over how great a distance, and how long the wind blows. The greater each of these factors is, the bigger a wave will be. Some of the biggest waves occur with hurricanes. A hurricane is a storm that forms over the ocean. Its winds may blow more than 150 miles per hour! The winds also travel over long distances and may last for many days.
    ::海洋波的大小取决于速度、距离、风吹的长度。 这些因素越大, 海浪就越大。 有些最大的海浪是飓风造成的。 飓风是横跨海洋的暴风, 风每小时可能吹150英里以上。 风也长途飘移, 可能持续许多天。

    Breaking Waves
    ::断波波

    As waves move into shallow water, they start to touch the land at the bottom. The waves drag and slow. Soon, the waves slow down and pile up. They get steeper and unstable as the top moves faster than the base. When they reach the shore, the waves topple over and break.  Figure    shows what happens to waves near shore. 
    ::随着海浪向浅水移动,海浪开始触碰海底的土地。海浪拖慢。很快,海浪放慢并堆积起来。随着顶部的移动速度比底部更快,海浪会更加陡峭和不稳定。当海浪到达岸边时,海浪会翻转和破裂。图显示海岸附近的海浪会怎样。

    Breaking waves

     

    Waves break when they reach the shore.
    ::海浪到达岸边时断裂

    Tsunamis
    ::海啸海啸海啸

    Not all waves are caused by winds. A shock to the ocean can also send waves through water. A tsunami is a wave, or set of waves, that is usually caused by an earthquake. As we have seen in recent years, the waves can be enormous and extremely destructive. Tsunamis can travel at speeds of 800 kilometers per hour (500 miles per hour). Usually tsunami waves travel through the ocean unnoticed.
    ::并非所有的海浪都是由风造成的。 海洋的冲击也可以通过水流发出波浪。 海啸通常是地震造成的波浪或波浪。 正如我们近年来所看到的那样,海浪可能是巨大和极具破坏性的。 海啸可以以每小时800公里的速度(每小时500英里)行驶。 通常海啸的波浪可以不为人所注意地穿过海洋。

    Tsunami waves have very small wave heights. In contrast, they have very long wavelengths. If you were at sea, you would not notice it pass under your ship. But when they reach the shore they become enormous. Tsunami waves can flood entire regions. They destroy property and cause many deaths.  Figure    shows the damage caused by a tsunami from the Indian Ocean in 2004.
    ::海啸波有很小的海浪高度。 相反,海浪的波长非常长。 如果你在海上,你就不会注意到海浪在船下经过。 但是当海浪到达岸边时,海浪会变得巨大。海啸波会淹没整个地区,摧毁财产,造成许多人死亡。图显示2004年印度洋海啸造成的损失。

    lesson content

     

    A 2004 tsunami caused damage like this all along the coast of the Indian Ocean. Many lives were lost.
    ::2004年的海啸给印度洋沿岸各地造成了如此严重的破坏,许多人丧生。

    Lesson Summary
    ::经验教训摘要

    • Most ocean waves are caused by winds.
      ::大多数海洋波浪都是由风引起的。
    • The size of a wave depends on how fast, how far, and how long the wind blows.
      ::海浪大小取决于风速、距离、风速、风速。
    • Tsunamis are waves caused by earthquakes.
      ::海啸是地震造成的波浪。

    Lesson Review Questions
    ::经验回顾问题

    Recall
    ::回顾

    1. Identify two causes of ocean waves.
      ::查明海浪的两个原因。
    1. What factors determine how big a wave is?
      ::是什么因素决定了波浪有多大?

    Apply Concepts
    ::应用概念

    1. The crest of an ocean wave is 3 meters above the still water level. The trough is 3 meters below the still water level. The horizontal distance between the crest and trough is 8 meters. Draw a diagram of this wave. Label the crest, trough, and distances. Then calculate the wave's amplitude and wavelength.
      ::海洋波的顶部在静水水平上方3米。 底部在静水水平下方3米。 顶部和底部之间的水平距离是8米。 绘制这一波的图示。 标出顶部、 底部和距离。 然后计算波的振幅和波长 。

    Think Critically
    ::仔细仔细思考

    1. Explain why waves break on the shore.
      ::解释为什么海浪在岸上爆发