One of the important questions for any educator is, "How can I teach difficult and abstract concepts in a way that connects with students' real life?". This is especially true in the senior years, when students are often confronted with ideas that don't appear relevant to their lives, are primarily explainable using mathematics rather than everyday language, and/or use equipment that students have never seen before, and will possibly never see again. In Year 12 physics, students must develop an understanding of the nature of light. This includes interference and diffraction phenomena. To assist in developing this understanding, many students undertake practicals in which diffraction gratings are used to produce a series of bright points of light and, by measuring this pattern and using mathematics, students can calculate the wavelength of the light producing the pattern. This article features an activity that enables students to produce a reasonably accurate measurement from something that is near and dear to their hearts-their phone. It also provides a good opportunity to practice mathematical calculations (conversion of units, mathematical manipulations, etc.), and to identify and discuss possible errors in an experimental procedure.