described in the previous section. The students were of middle level in physics
according to the evaluation of their schoolteachers. They possessed just basic
knowledge on geometric and wave optics (Young experiment), on wave’s phenomenology (quantities characterizing a wave, equation of a plan wave, concepts of
superposition of waves and interferences) and no experience in lab.
18.3.3 Monitoring Tutorials/Tools and Methodology
of Analysis
The students learning paths in the stages 1 and 3 were monitored using two tutorials.
The first tutorial suggests to students the following explorative challenges: (T1A)
Preview the light pattern on the screen when light passes a single slit width 1 cm and
another slit width less than 1 mm, (T1B) after observing the light diffraction pattern
produced by red light diffracted by a 0.12 mm slit, students were requested to draw
the pattern, to describe it, to sketch the corresponding light intensity vs position
graph expected, describing the main characteristics of that graph; (T1C) exploration
of how the diffraction pattern is affected by the change of parameters of the systems
(D, λ, a); (T1D) design a quantitative experiment aimed to extract the phenomenological laws of diffraction; (T1E) design a data analysis.
The second tutorial is divided into two parts. The first follows the suggestions of
McDermott group (2012), asking: the minimum distance between two sources to
obtain (T2A1) only a single (minima) nodal line or (T2A2) only one line of maxima
(besides the axis); (T2A3) assuming |F1 À F2| ¼ 6λ, which relation among PF1, PF2
and λ provides the set of the maximum interference points of order 2? Condition to
have second order maximum; (T2A4–5) Constructive interference points for arbitrary distance between sources. The second part proposed to students the following
questions: (T2B1) How do you write the equation of a wave? (T2B2) What does it
mean to superpose two waves? (T2B3) What does it mean to “sum up” two waves?
(T2B4/T2B5) Role of time and spatial parts of the phase wave to obtain a stable
interference pattern.
The analysis of students’ answers to the tutorial questions followed the qualitative
research criteria (Erickson 1998), distinguishing between interpretative and descriptive explanations, models underlay interpretation; conceptual references adopted.
The categories were defined a priori, according the previous research outcomes
(Michelini et al. 2014), and then redefined a posteriori, assuming typical students’
answers as operative definition of categories.
18 Student Learning Paths from Exploration of Optical Diffraction with Online. . .
227
according to the evaluation of their schoolteachers. They possessed just basic
knowledge on geometric and wave optics (Young experiment), on wave’s phenomenology (quantities characterizing a wave, equation of a plan wave, concepts of
superposition of waves and interferences) and no experience in lab.
18.3.3 Monitoring Tutorials/Tools and Methodology
of Analysis
The students learning paths in the stages 1 and 3 were monitored using two tutorials.
The first tutorial suggests to students the following explorative challenges: (T1A)
Preview the light pattern on the screen when light passes a single slit width 1 cm and
another slit width less than 1 mm, (T1B) after observing the light diffraction pattern
produced by red light diffracted by a 0.12 mm slit, students were requested to draw
the pattern, to describe it, to sketch the corresponding light intensity vs position
graph expected, describing the main characteristics of that graph; (T1C) exploration
of how the diffraction pattern is affected by the change of parameters of the systems
(D, λ, a); (T1D) design a quantitative experiment aimed to extract the phenomenological laws of diffraction; (T1E) design a data analysis.
The second tutorial is divided into two parts. The first follows the suggestions of
McDermott group (2012), asking: the minimum distance between two sources to
obtain (T2A1) only a single (minima) nodal line or (T2A2) only one line of maxima
(besides the axis); (T2A3) assuming |F1 À F2| ¼ 6λ, which relation among PF1, PF2
and λ provides the set of the maximum interference points of order 2? Condition to
have second order maximum; (T2A4–5) Constructive interference points for arbitrary distance between sources. The second part proposed to students the following
questions: (T2B1) How do you write the equation of a wave? (T2B2) What does it
mean to superpose two waves? (T2B3) What does it mean to “sum up” two waves?
(T2B4/T2B5) Role of time and spatial parts of the phase wave to obtain a stable
interference pattern.
The analysis of students’ answers to the tutorial questions followed the qualitative
research criteria (Erickson 1998), distinguishing between interpretative and descriptive explanations, models underlay interpretation; conceptual references adopted.
The categories were defined a priori, according the previous research outcomes
(Michelini et al. 2014), and then redefined a posteriori, assuming typical students’
answers as operative definition of categories.
18 Student Learning Paths from Exploration of Optical Diffraction with Online. . .
227