This research included three phases: investigation of college students' understandings of light and optics, development of multimedia activities, and assessment of students' learning. In the first phase, a quantitative method was used to analyze students' free responses and to obtain a general picture of students' knowledge about light and optics. Based on this analysis, semi-structured interviews were designed to more fully investigate students' understanding of the wave nature of light. The interview protocol included both double and single slit phenomena. Each interview included three parts: prediction and explanation of what would happen, observation and description of what actually happened, and explanation of the observed phenomena. The second phase of the research was the design of five multimedia activities to teach light and optics based on a contructivist model. These activities were entitled (1) Light - Going and Coming, (2) Bending of Light, (3) The Amazing Eye, (4) The Wave Property of Light #1, and (5) The Wave Property of Light #2. Three stations were implemented in the multimedia activities, including hands-on, interactive video, and microcomputer-based lab stations. The third phase of the research was the comparison of pre and post tests and oral interviews. The assessment shows considerable improvement in students' understandings of the optical concepts taught in the multimedia activities.