Activity #2: Slinky Waves

A Slinky can easily demonstrate the two basic types of waves, longitudinal and transverse, as well as several others. A longitudinal wave vibrates parallel to (in the same direction of) wave travel (sound waves are a good example). A transverse wave vibrates perpendicular (at right angles) to the wave travel (water waves are a good example).

To demonstrate the types of waves:

Have two students each take one end of a Slinky and stretch it out along the floor (the waves will be more apparent this way).

Longitudinal Waves. Have one student grasp and draw toward himself or herself several coils of a stretched metal Slinky and then release the coils. The other student must hold his or her end of the Slinky still. A longitudinal wave pulse will be generated and travel down the length of the Slinky.

Transverse Waves. Have one student move his or her end of a plastic or metal Slinky back and forth (left and right, like a snake crawling), perpendicular to its stretched length. The other student must hold his or her end of the Slinky still. A series of transverse waves will be generated.

Standing Waves. When a series of wave pulses are sent through a medium and then reflected back upon themselves, standing waves can be generated, as demonstrated in the space shuttle footage in the video, Slinky Scientific Shindig. These distinctive waveforms have places where the medium does not vibrate at all, called nodes, and other places where the medium vibrates the most, called antinodes. When the students are demonstrating transverse waves, standing waves with varying numbers of nodes and antinodes can be generated by having the student moving the Slinky vary the rate at which he or she continually moves it back and forth.

Compressions and Rarefactions. Longitudinal waves can be composed of compressions, where the parts of the medium (coils of the Slinky) are closer together than normal, or rarefactions, where the parts of the medium are farther apart than normal. In the above demonstration, the students created compressional longitudinal waves. A rarefactional longitudinal wave can be produced by stretching a segment of the Slinky and then releasing it.

The stretched area (rarefaction) will then travel along the length of the Slinky.

Activity No. 2 and graphics provided by Granger Meador, physics teacher, Bartlesville (Oklahoma) High School.



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Last Updated: 02/16/03
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