This probe investigated childrens' initial ideas about the position of a virtual image of a plane mirror and the position of the image due to refraction. Also this study examined the development of those ideas during constructivistic instructions and after these instructions. Data showed that at the beginning half of the students believed that the position of the image is on the mirror without using diagrams and the image due to refraction is in the same position with the object. During the instructions all students adopted gradually the scientific model. During the exercises all students used diagrams and posed the image behind the mirror but only half of the students were accurate. The posttest shows that most students continue to adopt the scientific ideas (only 3 students believe that the image is on the surface of the mirror and that the image due to refraction is at the same position with the object).