18. A pebble drops straight down into a tub of water, setting off ____________________ waves that travel at the boundary between the water and air. (1 point)
What are your choices?
circular
surface waves
The waves that are set off by the pebble dropping into the tub of water are called surface waves or water waves. These waves travel along the boundary between the water and the air.
To understand why these waves are formed, we can consider the principle of wave propagation. When the pebble drops into the water, it displaces the water molecules, causing a disturbance. This disturbance then spreads out in all directions as a wave.
To visualize this, imagine dropping a stone into a pond. When the stone hits the water, it creates a series of concentric ripples that spread outwards. These ripples are the surface waves.
Similarly, when the pebble drops into the tub of water, it creates waves that propagate along the water-air boundary. These waves are visible as the water surface rises and falls in a circular motion around the point of impact.
So, in summary, the pebble dropping into the tub of water sets off surface waves or water waves that travel at the boundary between the water and air.