Several studies have revealed that students have difficulty in understanding some aspects of image formation and observation in optics. Along with the identification of these difficulties in students’ minds, the possible sources of these difficulties should be determined. Teachers are considered as one of the most crucial source of student conception, for this reason studying teachers’ conception is important to understand student conceptions. In introductory optics students may not recognize the role of the observer and the screen in the image formation and observation. Several studies have been conducted on understanding image formation and observation in several grade levels (Bendall, Goldberg & Galili, 1993; Colin & Viennot, 2001; Galili, 1996; Galili & Hazan, 2000; Goldberg & McDermott, 1986, 1987; Wosilait, 1996), but the number of in-depth studies on pre-service teachers is limited. For this reason in the present study semi-structured interviews will be conducted with two pre-service physics teachers about their conceptualization of image formation and observation process. During the interviews pre-service teachers will be asked about the role of observer and the screen in different situations in image formation and observation processes. So the research question of this study is: •How do pre-service physics teachers conceptualize image formation and observation in different optical systems? With this study, two pre-service teachers’ conceptions in image formation and observation including the role of observer and screen will be categorized and discussed with comparing to other previous studies in similar tasks.

With this aim a qualitative research methodology with in-depth inquiry will be used. Since the main aim of the study is to elicit students’ conceptions, in-depth interviewing will be used as a method for collecting data. In the present study two pre-service physics teachers at Middle East Technical University (METU) who have already completed “Optics and Waves” course will be interviewed about the real image formation and observation in optical systems. Semi-structured individual interviews will be conducted in an approximately 40-minute period per student. The interview sessions will be videotaped and transcribed for in-depth analysis.

Although, generalizability is a problem for qualitative studies, they provide deeper information about participants’ conceptions. With this study, two pre-service teachers’ conceptions in image formation and observation including the role of observer and screen will be categorized and discussed with comparing to other previous studies in similar tasks. Some suggestions to teacher education programs for scientific conceptions of students will also be provided.