Standing Waves in an Elastic Spring: A Systematic Study by Video Analysis

The word “wave” is part of the daily language of every student. However, the physical understanding of the concept demands a high level of abstract thought. In physics, waves are oscillating variations of a physical quantity that involve the transfer of energy from one point to another, without displacement of matter. A wave can be formed by an elastic deformation, a variation of pressure, changes in the intensity of electric or magnetic fields, a propagation of a temperature variation, or other disturbances. Moreover, a wave can be categorized as pulsed or periodic. Most importantly, conditions can be set such that waves interfere with one another, resulting in standing waves. These have many applications in technology, although they are not always readily identified and/or understood by all students. In this work, we use a simple setup including a low-cost constant spring, such as a Slinky, and the free software Tracker for video analysis. We show they can be very useful for the teaching of mechanical wave propagation and the analysis of harmonics in standing waves.