Artifacts A and B show student responses to Question #4. The two pictures in Artifact A are good samples of the change in one variable – amplitude – but notice how the students’ interpretation of the change is connected to the “space between the sound waves.” Perhaps this is due to the less-defined bands of light and dark, but the wave property described by these students is not amplitude but rather frequency. Artifact B provides two similarly contrasting pictures, but the students’ explanation pays closer attention to the “movement of particles,” which supports a stronger understanding of amplitude for a compression wave. 

Note, too, how the description of wave “height” and “length” are conceptually challenging to apply to the physical representation of a compression wave, so Artifact B uses these terms analogously (“Consider it as being more like…”). These terms more clearly apply to the physical representation of a transverse wave or to mathematical models that plots a particle’s displacement versus time (for either compression or transverse waves).

Artifacts C, D, E, and F show student responses to Question #5. Interestingly, each artifact describes frequency from a different perspective. Artifact C identifies that higher frequency means that the waves “go faster and closer” (the images reveal that these students altered two variables at the same time, and is likely why they misattribute the wave property of being “slower and further apart” to amplitude rather than lower frequency). In a similar vein but with different words, Artifact D identifies that higher frequency means that the waves “become thinner [and] move more quickly.” Both of these attend primarily to the macroscopic bands that represent each wave. Artifact E connects this macroscopic perspective – described as “individual peaks and troughs” – with the microscopic perspective of how particles are moving. Artifact F connects the frequency of a sound wave to its physiological interpretation as pitch (or tone). 

Across these artifacts, only Artifact F mentions energy directly, but even here it is vaguely stated. The connection between amplitude, frequency, and energy is an inferential step that is not evident in any of these artifacts. This connection could be aided by considering the degree to which the particles of the medium are moving – in this case, the total kinetic energy transferred from the speaker source to the air particles surrounding it. 

The video of Artifact G shows students engaging in sensemaking around these ideas of wave properties. In particular, pay attention to how the conceptual understanding of waves as “vibrations” aids students connecting this to how compression waves travel through a medium (“chain reaction”) and how the material of the medium may impact wave properties.