Abstract:

An educational itinerary is shown here, developed with IBSE methodology and submitted to Italian students in latest year of a Secondary School during the Covid-19 period 2020/2021 i.e. in Distance Learning lessons.

The focus has been to aim what is the behavior of mechanical waves and highlight stationary waves. The startup point has been an engagment topic like a Chladni Patterns video and the inquiry questions “Why you can see these figures? Can you explain me why there are these shapes?”.
This educational itinerary introduces the concept of mechanical waves and narrows the field to periodic waves up to the phenomenon of standing waves. Thus it will be possible to explain the Chladni pattern phenomenon through the introduction of one-dimensional transverse waves that can add up along a plane in two-dimensional waves to form the characteristic figures initially observed.

This itinerary consists in three different step-lessons.
At first step there is a Chladni’s Patterns video to engage and to inquiry about student’s knowledge regard to focus contents (mechanical waves and stationary waves).

At second step, two laboratory experiments are foreseen about the generation of standing waves on a vibrating string and on a vibrating spring. These experiments in 2021 made in videos that showed the creation of transverse and longitudinal standing waves. This is because all the lessons were carried out in Distance Learning in Covid-19 period (2020/2021). In this way, the creation of transverse and longitudinal standing waves at different vibration frequencies of the two materials (rope and spring) was highlighted and visualized in the videos to carry out virtual laboratory lessons. So the authors carried out virtual laboratory lessons using videos and films of measurements made in the laboratory for the students before each lesson and substituted to the live experiments. From these videos the students had to perform the measurements required in the two experiments (of vibrating string and vibrating spring) to identify the resonant frequencies to generate the various harmonics. Anyway these students in this laboratory itinerary were guided in the laboratory practice of collecting and processing data and measurements.

Infact at third step, the experience about one-dimensional stationary waves are used to explain Chladni figures as stationary waves on a two-dimensional material. But in this section are used animation-gif to show like two-dimensional standing waves form Chladni's figures when salt or sand is placed on the vibrating iron platform.

Furthermore, with the above animations, it is highlighted that the nodes (in one-dimensional waves) become nodal lines (in two-dimensional waves) and these lines accumulate salt because they are formed where there is no movement and are separated by vibrating regions with phase opposite without salt build-up. These lines are nodal lines and their patterns are called Chladni figures.

At the end, this circular educational itinerary takes the students back to the initial question and makes them ready to give an autonomous answer to the initial submitted question.

Its advantage is to create a compelling type of educational itinerary on a topic that may be too abstract or less fascinating than other physics topics. And, last but not least, the advantage of using a virtual laboratory through videos at a time when it is difficult to relate to the laboratory lessons.

Keywords:

Virtual laboratory, Stationary Waves, Chladni Figures, Nodal lines.