Abstract:

Transverse and longitudinal waves are important issues in the physic subject of the senior high school. Generally speaking, the behavior of the transverse and the longitudinal waves can be presented by a spring. However, it is very difficult to show the wave behavior of sound and the mechanical characteristics of a rope wave. Here we propose a series of teaching methods to demonstrate the characteristics of waves, including the Beat effect, the Doppler effect and the standing wave. Moreover, in order to make the experiment can be carried out in the general classroom, popular Arduino electronics as a carrier and mobile apps as a remote control were used, thus greatly simplifying the required equipment.

First, a spring was used to demonstrate the transverse and longitudinal waves. At this time, the relationship between frequency, wavelength and wave velocity will be defined. Using the Arduino motherboard, the beat effect can be generated as two similar frequencies produced by two buzzers. This experiment was used to verify the wave behavior of sound. The Doppler effect is also a way to demonstrate the wave behavior. Therefore, a mobile app was used to simulate the sound of an ambulance heard by the listener. The app can manipulate the speed and acceleration of the ambulance and the distance between the listener and the ambulance. Finally, with the Arduino mainboard, a motor, an ultrasonic sensor, an optoelectronic switch, a cotton rope and weights, we demonstrated the standing waves with different tensions (F) and wavelengths (L). If the standing wave approximates a circular motion, we can see that F/(L^2) is a certain value. The experimental parameters including the frequency and the tension can be well manipulated by the mobile app. The wavelength of the wave was measured by the ultrasonic sensor. The experimental setup is quite small and easy to use in the classroom.

The teaching process mentioned above has been actually taught in middle school and high school in Taiwan. Students generally accept the Beat effect and the Doppler effect. The standing wave experiment is suitable for the high school students. It takes about 1 hour for the students to be familiar with the operation of the experiment and get reasonable experimental data. Therefore, these small Arduino experiments which remote controlled by the mobile apps were suitable for use in the general classroom. In addition, these experiments can make students interested in the application of electronic components and they are also conducive to the promotion of the STEM education.

For a long-term teaching schedule, the sensing principle of the electronic elements can be involved. This helps students to understand the underlying physical mechanisms of sensing. For programming, simple Arduino electronics and mobile apps can also be part of teaching activities. Due to the wide breadth of the learning activities, including electronics, physics, and programing, the experimental designs with miniaturized electronic components controlled by mobile apps will become one of the important way for teaching in the future. It is quite worth for teachers to pay attention and design such experiments.

Keywords:

Arduino, wave, velocity, tension, frequency.