This paper extends prior research on student use of computer simulations (sims) to engage with and explore science topics, in this case wave interference. We describe engaged exploration; a process that involves students actively interacting with educational materials, sense making, and exploring primarily via their own questioning. We analyze interviews with college students using PhET sims in order to demonstrate engaged exploration, and to identify factors that can promote this type of inquiry. With minimal explicit guidance, students explore the topic of wave interference in ways that bear similarity to how scientists explore phenomena. PhET sims are flexible tools which allow students to choose their own learning path, but also provide constraints such that students' choices are generally productive. This type of inquiry is supported by sim features such as concrete connections to the real world, representations that are not available in the real world, analogies to help students make meaning of and connect across multiple representations and phenomena, and a high level of interactivity with real-time, dynamic feedback from the sim. These features of PhET sims enable students to pose questions and answer them in ways that may not be supported by more traditional educational materials. (Contains 5 figures.)