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新概念英语第四册美音版040:Waves 海浪

kira86 于2016-04-08发布 l 已有人浏览

Lesson 40 Waves

First listen and then answer the following question.

What false impression does an ocean wave convey to the observer?

Waves are the children of the struggle between ocean and atmosphere, the ongoing signatures of infinity.

Rays from the sun excite and energize the atmosphere of the earth, awakening it to flow, to movement, to rhythm, to life.

The wind then speaks the message of the sun to the sea

and the sea transmits it on through waves--an ancient, exquisite powerful message.

These ocean waves are among the earth's most complicated natural phenomena.

The basic features include a crest (the highest point of the wave),

a trough (the lowest point), a height (the vertical distance from the trough to the crest),

a wave length (the horizontal distance between two wave crests),

and a period (which is the time it takes awave crest to travel one wave length).

Although an ocean wave gives the impression of a wall of water moving in your direction,

in actuality waves move through the water leaving the water about where it was.

If the water was moving with the wave,

the ocean and everything on it would be racing in to the shore with obviously catastrophic results.

An ocean wave passing through deep water causes a particle on the surface to move in a roughly circular orbit,

drawing the particle first towards the advancing wave, then up into the wave,

then forward with it and then--as the wave leaves the particles behind--back to its starting point again.

From both maturity to death, a wave is subject to the same laws as any other 'living' thing.

For a time it assumes a miraculous individuality that, in the end, is reabsorbed into the great ocean of life.

The undulating waves of the open sea are generated by three natural causes:

wind, earth movements or tremors, and the gravitational pull of the moon and the sun.

Once waves have been generated,

gravity is the force that drives them in a continual attempt to restore the ocean surface to a flat plain.
 

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