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Comment: 02:35 - 03:59 (01:24)
Source: Annenberg/CPB Resources - Earth Revealed 24, Waves, Beaches and Coasts
Keywords: "ocean wave", beach, energy, ripple, wind, crest, trough
Our transcription: When a wave approaches the beach, it's not the water itself that's advancing, but a surge of energy which is moving through the water.
It's like the ripple that runs across a field of grain when the wind blows.
The individual stalks don't run across the field; they simply bend as the wind strikes them.
Or take the wave at a football game which creates the allusion that the spectators are rippling around the stadium when all they're actually doing is standing up or sitting down.
The same principle applies to water waves.
Consider what happens to a floating object as a wave of energy passes through the water.
That object tends to stay more or less in the same place tracing a circular motion as it bobs up and down.
The individual particles composing the wave behave in a similar way.
As the crest of the wave arrives, it lifts the particle up and forward, and then when the trough of the wave follows, the particle falls down and backward.
Like the stalk of grain or the football fan, the particle returns to its original position after the disturbance is passed.
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