New trends in physics teaching, v.4; The ... - unesdoc - Unesco

New Trends in Physics Teaching IV
Figure 7.
Conclusion
The children’s ideas about the visual perception of any object can be summed up by the following
diagrams (figures 8 to 11):
obiect obiect obiect
Figure 8.
Figure 9. Figure 10.
Figure 11.
Figure 8 shows the ‘ambient light’: no interconnection is seen between the eye, the light and the
object. In the case of figure 9, once again the need for a link between the eye and the object is
not recognized by the child, but the light has a more precise role: it lights up the object. These
two diagrams are equally representative of the ideas formed by the very large majority of the
children. For, as we saw, very few children imagined ‘sight’ to be a movement, represented
diagramatically in figure 10, going from the eye to the object, and the explanation given by
physicists, represented in figure 11, was very seldom put forward by the children, especially
in the case of objects that were not luminous in themselves. This is connected with the fact that
they do not suspect that objects reflect light.
These ideas about vision are important on their own account: the explanation given by the
physicist, who considers the eye to be light-receptive, is not a part of established knowledge.
One of the aims of education must be to make that explanation known. These ideas about vision
are also important with regard to the validity of certain standard experiments carried out in
physics classes. In the field of optics, for instance, many courses begin by establishing that light
is propagated in a straight line, and this is done by carrying out the following experiment: it is
demonstrated to the pupil that he cannot see a candle flame through a series of cardboard sheets
with holes, unless the holes are in a straight line [5]. To apply this observation, the path of a
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