This article illustrates a learning sequence from the Interdisciplinary Mathematics and Science (IMS) Learning project, connecting science and mathematics learning in the primary school. Exploring light and its properties involved a series of investigations conducted in Grades 4 and 5 across three classes in two schools in regional Victoria. The teachers implemented an inquiry-based pedagogical model to guide students' spatial reasoning by exploring angle, symmetry, rotation, 2D diagrams and 3D models in an investigation of light reflection, using multiple representations. Students developed ideas from a "maze challenge" used in their design of a periscope.