Decha SuppapittayapornBhinyo PanijpanNarumon EmaratMahidol University2018-09-242018-09-242010-04-01Physics Teacher. Vol.48, No.4 (2010), 256-257194349280031921X2-s2.0-85007363707https://repository.li.mahidol.ac.th/handle/123456789/29953After learning how to trace the principal rays [Fig. 1(i)] through a thin lens in order to form the image in the conventional way, students sometimes ask whether it is possible to use other rays emanating from the object to form exactly the same image-for example, the two arbitrary rays shown in Fig. 1(ii). The answer is a definite yes, and this paper presents a method of doing so.Mahidol UniversityPhysics and AstronomySocial SciencesArticleSCOPUS10.1119/1.3361997