Abstract
The single-quantum double-slit experiment is often taught through a compact narrative of localised detections, interference, and wave–particle duality that may conceal weak explanatory coordination. This qualitative-dominant mixed-methods study investigates how students and teachers distinguish description of the experimental outcome from recognition of its interpretative problem. The framework uses counterfactual model testing as an analytical lens for examining model–evidence coordination, together with epistemic framing, ontological flexibility, and multimodal representation. The study draws on 54 individually coded questionnaires from the “100 QM” course and six follow-up interviews. In this corpus, 48 participants (88.9%) adequately described the double-slit outcome, whereas 26 (48.1%) also articulated, in response to the questionnaire prompts, a specific explanatory tension or unresolved relation concerning the experimental outcome. Recurrent explanations invoked definite trajectories, literal wave–particle transformations, physicalised probability waves, appeals to self-interference, and anthropocentric observation. The findings indicate that descriptive familiarity and technical terminology do not by themselves ensure interpretative recognition. These findings reinforce the distinction between descriptive familiarity and interpretative understanding, showing that understanding the double-slit experiment involves not only descriptive adequacy, but also the recognition and examination of the explanatory tensions that emerge when proposed models are compared with the experimental evidence.