The resonance of sound and light: a model for two different phenomena

Cristiano Lino Fontana1, Sandra Moretto 1, Stefania Lippiello2, Antonella Maddalozzo2
1Department of Physics and Astronomy “Galileo Galilei,” University of Padova, Italy
2 Liceo Scientifico Statale “Jacopo da Ponte”, Bassano del Grappa (VI), Italy

Background

In the Italian secondary school system, the students are obliged to take a final exam at the end of the 13th grade. The final exam is undergoing a change of the syllabus as well as the modality [1]. The new exam is more focused on the disciplines that characterize the school curriculum. For schools with a scientifically oriented curriculum, the final test is shifted from a math-only test to a physics and math test. Therefore it is important to focus the learning paths on core ideas that are fundamental for the new final evaluation. Modelization and the experimental competences should be enhanced and they should be introduced early on, in the students’ careers. We want to focus on the Physics of Waves as a core idea [2] and as a model of classical physics (compared to the particle model). The approach is to describe a behavior that is common to two very different phenomena, in order to underline the common theoretical framework. Thus we want to address the resonance of physical systems both for sound waves and for electromagnetic waves (specifically in the visible spectrum).

Implementation

This learning activity is carried out in parallel with two different classes of the 12th grade. First, the students are introduced to the simple harmonic motion, in order to give the first example of oscillatory motion. Then wave dynamics is introduced from a more abstract point of view. As the underlying laws are the same for sound and light, the phenomenon of the resonance is shown in both the physical systems. Starting from the sound, two tuning forks are used to demonstrate the resonance between the two. Their vibration is also stimulated with an audio speaker. Moving on to the light, the resonance between LEDs of different colors is shown. The LEDs are used both as light emitters and as light detectors. The detecting LEDs produce a higher response when stimulated with an emitter with a matching color. Students are asked to describe the two models and to emphasize the underlying principles. Conclusions With this activity, we experiment on phenomena associated with theoretical concepts learned in class. This eases a deeper understanding of the concepts and it emphasizes the importance of having a model. At the same time, students’ experimental competencies are trained as well. We show that there is a common model for different phenomena, even if they are perceived as very different systems. Moreover, carrying out the activity in two classes helps in understanding the strengths and the weaknesses of the activity.

References

[1] MIUR, “Esame di Stato conclusivo dei percorsi di istruzione secondaria di secondo grado a.s. 2018/2019 – prime indicazioni operative“. Circolare ministeriale 3050, 4/10/2018
[2] National Research Council 2012. “A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas”. Washington, DC: The National Academies Press. DOI:10.17226/13165.