What Happens When a Wave Hits a Surface?

We had another mini-experiment:
What happens when a wave hits a surface?
To do this experiment, we had a large blue piece of paper against a wall, and many different malls. I was partnered up with Maria. We wet the balls with water, and them rolled them so they hit the wall and bounced off, all while leaving a trail of water on the paper. We immediately went over the trail with a marker so we could see the trail after it was dry, and labelled what ball we used to make the trail with. Most of the time the trails looked like an upside-down V, because the ball would roll, collide with  the wall, and bounce back at an angle. That angle depended on the angle from which the ball was thrown.
We noticed a few things. First of all, the harder you roll the ball, the straiter and more consistent the line would be. Also the impact and resulting bounce off of the wall was shorter and louder with a harder roll. (That was obvious.) More about the impact: The ball always bounced off cleanly, but lost some of the energy which caused it to slow down.
Update:
After reading the textbook section, I have a new conclusion:
I found out that the angle that the angle bounced is the same angle as the ball came in, just from the other way. That didn't make much sense, so I made a illustration on a keyboard.


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The line represents the wall, and the upside-down V is the ball's path (or the closest approximation that I could show with text).
If you measured the angle from the wall to the closest line, it would be the same as the wall to the other closest line.
Using my new vocabulary, the angle of incidence was the same as the angle of reflection.