  An investigation on student understanding of waves is performed during an
optional laboratory realized in informal extracurricular way with few,
interested and talented pupils. The background and smart intuitions of students
rendered the learning path very dynamic and ambitious. The activities started
by investigating the basic properties of waves by means of a Shive wave
machine. In order to make quantitative observed phenomena, the students used a
camcorder and series of measures were obtained from the captured images. By
checking the resulting data, it arose some learning difficulties especially in
activities related to the laboratory. This experience was the starting point
for a further analysis on disciplinary knots and learning problems in the
physics of waves in order to elaborate a teaching-learning proposal on this
topic.
