Identifying a student's mental model is important for understanding scientific concepts. Dispersion and polarization are the sub concept of physics that studied in high school on light waves concept. This study aimed to develop dispersion and polarization conceptual inventory (DIPOLCI) to identify students' model mental using Rasch analysis. The research method utilized analyzing, designing, developing, implementing and evaluating (ADDIE) method. The participants involved 34 students (26 female and 8 male) from senior high school in Patokbeusi, West Java, Indonesia and their average 17-18 ages old. DIPOLCI consists of 7 items in the form of one tier and then developed to be four tiers test. DIPOLCI examined through Rasch analysis based on fit statistics, Cronbach Alpha, "item reliability" and "person reliability," and students' mental model. The results show that DIPOLCI were valid and reliable to identify students' mental model. Students' mental model are mostly in the synthetic (SY) and scientific (SC) mental models were also analyzed in this research. It can be concluded the developed of DIPOLCI was able to analyze students' mental model. Developing this test instrument allows teachers to pinpoint students' comprehension of fundamental light wave concepts, uncover misconceptions, and evaluate the efficacy of teaching methods. [Note: The page range (239-247) shown on the PDF is incorrect. The correct page range is 238-247.]