The purpose of this study was threefold: Examine middle school teachers' familiarity with, interest in, conceptual knowledge of and performance on light; Examine their ability to identify misconceptions on light and their suggested pedagogical ideas to address the identified misconceptions; and Establish the relationship between the middle school teachers' interest, familiarity, conceptual understanding, performance, misconception identification, and pedagogical ideas for light. Sixty six (66) middle school science teachers enrolled in three math and science teacher professional development projects at Southern Illinois University Carbondale participated in this study. This study used mixed-methods approach to collect and analyze data. The participants responded in writing to four different instruments: Familiarity and Interest Questionnaire, Conceptual Knowledge Test, Two-tier Performance Test, and Misconceptions Identification Questionnaire. Data was analyzed quantitatively by conducting non-parametric (Wilcoxon, Mann-Whitney U, and Kruskal-Wallis) and parametric (paired samples, independent samples, and One-Way ANOVA) tests. Qualitative data was analyzed using thematic analysis and open coding to identify emerging themes and categories. The results showed that the teachers reported high levels of familiarity with and interest in learning more about light concepts. However, they had low conceptual knowledge and performance on light concepts. As such, middle school teachers' perceived knowledge of light concepts was not consistent with their actual knowledge of light. To some extent, the teachers identified students' misconceptions expressed in some scenarios on light and also suggested pedagogical ideas for addressing such misconceptions in middle school science classrooms. However, most teachers did not provide details on their pedagogical ideas for light. Correlations among the four constructs (familiarity, interest, conceptual understanding, and performance) were only significant between performance and conceptual understanding, r (64) = 0.50, p = 0.000. There was no significant relationship between conceptual understanding and familiarity, and between performance and familiarity. In view of these findings, it is evident that some teachers did not have sound conceptual understanding and pedagogical ideas to effectively help their students develop the understanding of light concepts accentuated in the US national science education standards. These findings have implications on teacher education and science teaching and learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]