This analysis concerns the help given to students by a computer-based model, in the field of geometrical optics. We consider that physics learning is necessarily the establishment of links between two worlds, the world of objects and events, and the world of theory and models. Our study aims to understand whether the computer-based model has enriched these links in the verbal productions of students. We relate the resources given to students during a rather long teaching sequence, and the kinds of their verbal productions. The results show that the computer-based model has favoured the use of physics theory, with more efficiency than the performing of experiments. But the link with the world of objects and events needs accurate instructions from the teacher.