Being P-Waves and S-Waves
This material was originally created for Starting Point:Introductory Geology
and is replicated here as part of the SERC Pedagogic Service.
Modeling P-waves and S-Waves
Have the students get out of their chairs, move into groups of 10-15 in an area where they can stand together in a line standing shoulder to shoulder within their group with their arms across each-other's shoulders. For a P-wave, push the group from one end of the line. All the students will bend, but straighten. For an S-wave, have the person at the end of the line bend at the waist to almost a 90-degree angle and then to stand up straight again. This will force the next person, and then the next person, and so on to do the same.
An alternative way to do this activity is to have the whole class stand up together in a circle and do "the wave" as they would in a football stadium, raising their arms and lowering them as the next person raises his or hers. This is a transverse (S) wave. Then have them do a longitudinal (P) wave by having them gently grip each other's shoulders and having one pull or push the next person in line.
Rates and Reflection
Have student from outside the group measure how long it takes the given wave to propagate, and others to measure the distance. Explain that the time is the period and the distance is the wavelength. What are the frequency and the velocity of the wave? Can the students making the wave speed it up?
You may also want to designate a student in the middle of a chain or move the chain against a rigid surface like a wall to reflect waves. Instead of the wave continuing beyond the point of reflection, it must go back the way it came.
- Help students develop a good understanding of different kinds of seismic waves and their effects
- Liven up a lecture class (esp. for 8 AM sections)
- Demonstrate a quantitative idea (wave frequency)