Final answer:
In shallow water, water particles at the wave crest and those at the bottom of the wave move together vertically as the wave passes. The energy of the wave moves forward, but the particles remain in place, moving in a circular motion. Answer C) They move together is correct.
Step-by-step explanation:
In shallow water, the common misconception is that water waves push water from one direction to another, but in reality, the water particles tend to remain relatively in the same location, moving up and down in place with the energy of the wave. Therefore, the water particles in the wave crest are not ahead or behind those at the bottom of the wave; they move vertically as the wave passes. The correct answer to the question is C) They move together.
This vertical motion is due to the energy of the wave traveling forward while the particles stay mostly stationary. Waves have moving crests and troughs, with the crest being the highest point of the wave and the trough being the lowest. When waves approach the shore and enter shallow water, an effect known as shoaling occurs. The energy of the wave is compressed into a smaller volume as the water depth decreases, leading to higher waves but not necessarily moving the water particles forward.
Surfers riding waves are an example where this phenomenon might seem misleading, as they seem to ride on cascading water. However, they are actually utilizing the energy that moves forward across the water's surface, not moving with a flow of water that travels from the wave's origin to the shore. The water particles themselves create a pattern of movement, typically circular motions underneath the wave, where they return to their original position once the energy of the wave has passed.