How does the ping sound announce refracted rays?
Multiple seismic paths migrate downward to be critically refracted off of increasingly higher-velocity boundaries showing that although the deepest path is the longest, the transit time is less than the direct wave that travels entirely in the slow layer. AUDIO ARRIVAL SOUNDS.
Seismic waves travel at different speeds through different materials. In this 2-layer model two wave fronts leave an impact at the same time but the lower layer is faster.
Seismic waves travel a curving path through the earth due to changes in composition, pressure, and temperature within the layers of the Earth.
Animation shows the race between the direct seismic wave vs. the deeper, longer-path critically refracted seismic wave. Graph records the arrival times.
In this model of increasing velocity with depth, the critically refracted seismic rays speed up with depth as they pass 5 different velocity boundaries.
Like other waves, seismic waves obey the laws of physics. In this activity Physics students have the opportunity to apply their understanding of the basic concepts of waves (e.g. reflection, refraction and transmission of energy) as they examine seismic data to determine how far it is from the surface to the bedrock.