2. When the wind blows across the
water, it changes the water's
surface, first into ripples and then
into waves. Storms can make
enormous waves, particularly if the
wind, blows in the same direction for
any length of time. In this chapter,
you can learn what waves are and
how they behave.
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3. • waves and environment Waves have a major
influence on the marine environment and ultimately
on the planet's climate.
• wave motion Waves travel effortlessly along the
water's surface. This is made possible by small
movements of the water molecules. This chapter
looks at how the motion is brought about and how
waves can change speed, frequency and depth.
• wave groupsIn the real world, waves are not of an
idealised, harmonious shape but irregular. They are
composed of several interfering waves of different
frequency and speed.
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4. • waves and wind The wind blows over the water, changing
its surface into ripples and waves. As waves grow in height,
the wind pushes them along faster and higher. Waves can
become unexpectedly strong and destructive.
• waves in shallow water As waves enter shallow water,
they become taller and slow down, eventually breaking on
the shore.
• wave groups In the real world, waves are not of an
idealised, harmonious shape but irregular. They are
composed of several interfering waves of different
frequency and speed.
• wave reflectionWater waves bounce off denser objects
such as sandy or rocky shores. Very long waves such as
tsunamis bounce off the continental slope.
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5. • Waves in the environment
• Wave motion
• Waves and wind
• Waves entering shallow water
• Wave groups
• Wave reflection
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6. Waves in the environment
• Waves in the environment
Without waves, the world would be a different place. Waves
cannot exist by themselves for they are caused by winds.
Winds in turn are caused by differences in temperature on the
planet, mainly between the hot tropics and the cold poles but
also due to temperature fluctuations of continents relative to
the sea.
Without waves, the winds would have only a very small grip
on the water and would not be able to move it as much. The
waves allow the wind to transfer its energy to the water's
surface and to make it move. At the surface, waves promote
the exchange of gases: carbon dioxide into the oceans and
oxygen out. Currents and eddies mix the layers of water
which would otherwise become stagnant and less conducive
to life. Nutrients are thus circulated and re-used.
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12. Surf breaker are classified in 3
types
• Spilling breaker
• Plunging breaker
• Surging breaker
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13. Spilling breakers
Spilling breakers are a familiar sight on
most beaches. They arise from long
waves breaking on gently sloping
beaches. There are several rows of
breakers.
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14. Plunging breakers
Plunging breakers can occur on steeply sloping beaches.
There is only one row of breakers.
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15. Plunging breakers
Surging breakers surge over steeply sloping (but
not vertical) beaches or rocks. Waves break one at
a time.
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16. Parts of a Wave
• Picture of a Wave
• Crest and Trough
• Amplitude
• Wavelength
• Frequency
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17. Pictures of a wave
• In the above diagram the white line represents the position of the medium
when no wave is present. This medium could be imagined as a rope fixed at
one end a few feet above the ground and held by you at the other end.
• The yellow line represents the position of the medium as a wave travels
through it. We simply say that the yellow line is the wave. If we consider the
rope mentioned before, this wave could be created by vertically shaking the
end of the rope.
• Often, when several waves are traveling along a medium as shown above,
the continuous group of waves is called a wave train.
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18. Crest and Trough
• The section of the wave that rises above the
undisturbed position is called the crest. That
section which lies below the undisturbed position
is called the trough. These sections are labeled
in the following diagram:
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19. Amplitude
• The term amplitude can have slightly different meanings
depending upon the context of the situation.
• Its most general definition is that the amplitude is the
maximum positive displacement from the undisturbed
position of the medium to the top of a crest.
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20. Wavelength
• The wavelength of a wave is the distance between any
two adjacent corresponding locations on the wave train.
This distance is usually measured in one of three ways:
crest to next crest, trough to next trough, or from the start
of a wave cycle to the next starting point.
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21. • Actually, the a wavelength exists between any
point on a wave and the corresponding point on
the next wave in the wave train. A few of such
distances are shown.
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22. Frequency
• Frequency is often not termed as a part of
a wave, but it makes sense to introduce its
meaning in this section.
• Frequency refers to how many waves are
made per time interval. This is usually
described as how many waves are made
per second, or as cycles per second.
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