Final answer:
A sudden push of a plastic panel into the water forms an expanding disturbance called a wave, which can be observed when a drop of water generates outwardly traveling circular waves.
Step-by-step explanation:
When a plastic panel is pushed suddenly into the water, it creates an expanding disturbance in the water known as a wave. This phenomenon can be seen when a drop of water falls onto a smooth surface, generating a set of waves that travel outward in a circular direction. Waves are not only formed by such sudden actions but also by other factors such as wind, which can also create waves known as ripple marks on the surface of a body of water. These ripple marks are formed by the back-and-forth flow of water and are most commonly found in shallow marine environments.