How do waves react once they hit a surface?

In class, we have conducted an experiment to investigate how would waves react once they hit a surface. We used balls made out of different materials, and of different density to represent the waves. Against a wall, we put a piece of paper, and along we rolled ball after ball, tracing the path it takes once it hits the wall with a marker. All the balls were different density, and were made out of a different material. My partner for this lab was Aca.
 From what we have observed, balls will with different density will come back a different way, and will take a different path. The balls which have a lower density bounce on the wall, and come back on the similar path it was rolled on. As the different balls get more dense, they start going in the opposite angle/ direction from which they were rolled from. As I wrote above, when a wave hits a surface it cannot pass through, it will come back the way it came from.
From this lab I have learnt a lot, since before I have always thought that once a wave bounces into a surface, it will just automatically stop. This experiment helped me rah a conclusion that whn a wave hits a surface or barrier, it will deffinetely come back, but which way, and which speed, depends on the density and the properties of the wave.