Final answer:
The water around a drip moves due to waves traveling through it, which are generated when a drop impacts the surface. The patterns seen are because of interference between waves, and the amplitude generally decreases as the waves spread out from the source.
Step-by-step explanation:
The movement of water around a drip is caused by waves traveling through the water when a drop falls onto the surface. As a drop hits the smooth water surface, it creates an up-and-down disturbance, causing waves that move outward in a circular pattern. These are surface waves, which have distinctive crests (the highest point of the wave) and troughs (the lowest point).
These waves can sometimes display a complex pattern known as a criss-cross pattern, which is due to the interference of waves. When waves traveling in different directions meet, their crests and troughs can either reinforce each other, leading to a higher wave (constructive interference), or cancel each other out, resulting in a smaller wave or no wave at all (destructive interference).
When multiple drops hit the water or a pebble creates ripples, concentric circles are seen because each interaction with the water surface produces its own set of waves, and these can overlap to create complex patterns. Over time, the amplitude of these waves typically decreases as they move away from the source due to the spreading out of the wave energy over a larger area.