In a lov/ deep-v;ater wave the water particles move in circles. 

 At any depth, _z, below the surface the radius of the circular path 

 followed by a particle is 



r = £i e L 

 2 



In this circle the velocity is 



V = 2jrr ^ H ^'^'^f 

 T T 



because the particles complete one revolution in the time T (see 

 fig. 2) . 



A water particle at the sea surface remains at the surface 

 throughout its orbit, A water particle at a given average depth 

 below the sea surface is farthest from the surface when it moves 

 in the direction of wave progress. 



In a low shallow-water wave the vertical motion of the 

 particles is negligible and the horizontal motion is independent 

 of depth. The particles move back and forth, following nearly 

 straight lines. 



In a deep-water wave only half of the energy advances with 

 wave velocity, whereas in a shallow-water wave all the energy 

 advances with wave velocity. The reason for this difference is 

 that in a deep-water wave only the potential energy varies period- 

 ically and advances with the wave form, but in a shallow-water 

 wave both potential and kinetic energy vary periodically and both 

 advance with the v;ave form. These laws can also be stated by say- 

 ing that the energy advances at a rate which, in a deep-water wave, 



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