The big question is, how do we know about the composition of the earth's core? Sal explains that at 105 degrees from the source point of an earthquake, the phenomenon of the p wave shadow zone leads us to conclude that the waves are...

Mr. Khan uses the metaphor of a car to help explain the change in the direction of waves as they hit a boundary between two mediums. He then goes on to explain the relationship between the earth's structure and density and the waves'...

Use a video on seismic waves to explain the differences between S and P waves, as well as the details that they provide about the composition of the rock.

Starting with a clear diagram to demonstrate how a wave actually forms, an informative video will provide a great summary of s-wave travel. It explains the difference between polar bonds in liquids and the stronger ionic and covalent bonds.