Activity: Understanding the Doppler Effect

Materials:

one meter of vacuum cleaner hose, hand-out on the Doppler Effect, slinky

About this Activity

This activity involves teacher demonstrations and student demonstrations followed by class discussions about the Doppler effect. The activity using the vacuum cleaner hose represents the Doppler effect through sound. The activity with the slinky represents the Doppler effect by showing the change in wavelength as a body moves closer or farther away from an observer.

Procedure:

  1. Obtain a piece of vacuum cleaner hose about one meter in length. Rotate the hose above your head to produce two sounds of different pitches. Discuss student observations by asking the following questions:
  2. Pass out the hand-out on the Doppler effect and review it with your students.
  3. Have students get into pairs or in their lab groups. Their task is to design a demonstration using a slinky to illustrate the Doppler effect to check their understanding of the concept. Give students additional guidance depending on their ability level. If you have enough slinkies, you may want to give one to each group to allow them to experiment. Once all groups are finished, have them demonstrate and explain the Doppler effect using a slinky to the class.
  4. Students should have used the slinky to represent a wave. Each end of the slinky should be held by a student. Each student represents an observer. As one observer moves away from the other observer, the wavelengths should increase. As the observer moves closer to the other observer, the wavelengths should decrease. For example, as the wavelengths of a source increases, the object is moving away from the source. And as the wavelengths of a source decreases, the object is approaching the source.
  5. If students were not able to figure out how to demonstrate the Doppler effect, do procedure 4 as a demonstration to illustrate the concept.
[Doppler Effect handout]

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[LMGFP home page] Contact Karen Krupinsky (kgurley@gsfc.nasa.gov) or
Tammy Seergae (tseergae@umd.edu) for further information.