was requested to summarize the elements of this model. The students, rather than
describing the structure of the model by elements, responded by list the model
elements they had grasped or that had remained more impressed. More than half
(16/26) recalled some formal elements of the wave model (the equation of the
amplitude of a sinusoidal wave, the sum of amplitudes as an implementation of
the overlap, the average of the square of this amplitude to obtain the “intensity”)
without defining the symbols or explaining the meaning of the written equations, but
explaining most often the conditions of maximum/minimum interference (9/16) and
recalling other elements of the model such as the fact that the slit is much greater than
the wavelength of the light used.
18.5 Outcomes and Conclusion
A study carried out on how a sample of 186 high school students’ analysed the
phenomenology of light diffraction and how they passed from a geometrical, to a
wave model of light. Students in little groups explored light diffraction, in educational labs of operative exploration (Michelini 2006). Their conceptions on light
diffraction and learning paths were monitored using tutorials implementing IBL
strategy, analysed according to the qualitative research criteria.
Concerning, the students’ models activated by qualitative exploration of phenomena (RQ1), students looks initially at diffraction more often as a “light enlargement” (76%). The presence of maxima and minima, crucial for that phenomenology,
is not always recognized or is considered of second order by students, because a lack
in their physical or mathematical models of the phenomenon. This shows that the
students’ model affects strongly what they look at/observe. In accord with the
theoretical perspective of Karmiloff-Smith (1988) and other researchers (Chinn
and Brewer 2001), students “seen” the aspects that find meaning in their conceptual
model. A new model is needed to include unexpected features/data. In the CLOE
Lab, the overcoming of the first partial models activated was promoted thanks to the
discussion in large group, which allowed to share a complete picture of the observed
phenomenon.
Concerning the light intensity distributions expected by students before
performing the experiment, in half of cases they have drawn a bell/parabolic shape
graph or other form of envelope of the distribution (linear or inverse power). Two
profiles can be distinguished: The first profile includes students representing envelope distributions in accord to their representation of the diffraction pattern as a
unique large spot, and the second profile includes students representing an envelope
of the distribution, but having drawn the diffraction pattern as a discontinuous
sequence of points/lines. In this case, students were not able to activate a formal
model accounting both the periodic variation and the decreasing of the intensity. The
use of discontinuous distributions is another aspect of the same problem. The lack of
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A. Stefanel
describing the structure of the model by elements, responded by list the model
elements they had grasped or that had remained more impressed. More than half
(16/26) recalled some formal elements of the wave model (the equation of the
amplitude of a sinusoidal wave, the sum of amplitudes as an implementation of
the overlap, the average of the square of this amplitude to obtain the “intensity”)
without defining the symbols or explaining the meaning of the written equations, but
explaining most often the conditions of maximum/minimum interference (9/16) and
recalling other elements of the model such as the fact that the slit is much greater than
the wavelength of the light used.
18.5 Outcomes and Conclusion
A study carried out on how a sample of 186 high school students’ analysed the
phenomenology of light diffraction and how they passed from a geometrical, to a
wave model of light. Students in little groups explored light diffraction, in educational labs of operative exploration (Michelini 2006). Their conceptions on light
diffraction and learning paths were monitored using tutorials implementing IBL
strategy, analysed according to the qualitative research criteria.
Concerning, the students’ models activated by qualitative exploration of phenomena (RQ1), students looks initially at diffraction more often as a “light enlargement” (76%). The presence of maxima and minima, crucial for that phenomenology,
is not always recognized or is considered of second order by students, because a lack
in their physical or mathematical models of the phenomenon. This shows that the
students’ model affects strongly what they look at/observe. In accord with the
theoretical perspective of Karmiloff-Smith (1988) and other researchers (Chinn
and Brewer 2001), students “seen” the aspects that find meaning in their conceptual
model. A new model is needed to include unexpected features/data. In the CLOE
Lab, the overcoming of the first partial models activated was promoted thanks to the
discussion in large group, which allowed to share a complete picture of the observed
phenomenon.
Concerning the light intensity distributions expected by students before
performing the experiment, in half of cases they have drawn a bell/parabolic shape
graph or other form of envelope of the distribution (linear or inverse power). Two
profiles can be distinguished: The first profile includes students representing envelope distributions in accord to their representation of the diffraction pattern as a
unique large spot, and the second profile includes students representing an envelope
of the distribution, but having drawn the diffraction pattern as a discontinuous
sequence of points/lines. In this case, students were not able to activate a formal
model accounting both the periodic variation and the decreasing of the intensity. The
use of discontinuous distributions is another aspect of the same problem. The lack of
234
A. Stefanel