1724 USEJ 6 (3) (2017) Unnes Science Education Journal http://journal.unnes.ac.id/sju/index.php/usej FOUR-TIER DIAGNOSTIC TEST TO IDENTIFY MISCONCEPTIONS IN GEOMETRICAL OPTICS Qisthi Fariyani, Ani Rusilowati  , Sugianto Physics Education, Science and Technology Education UIN Walisongo Semarang Article Info ________________ Received July 2017 Accepted October 2017 Published December 2017 ________________ Keywords: diagnostic; four-tier test; Geometrical Optics; misconceptions ____________________ Abstract ___________________________________________________________________ The purpose of this research was to identify student misconceptions in Geometrical Optics. Four- tier multiple choice diagnostic test can be used to identify student misconseptions. The data of this research were obtained by interview, questionnaire, and test. This research used random sampling to 107 X grade students who already got Geometrical Optics materials. The data of this research were analyzed and interpreted to distinguish students who understand the concept, not understand, and misconceptions. Result of the research showed that on each item of test, there are some students who have misconceptions. Students had misconceptions in low category with details of 31% of all test item, 53% in medium category, and 16% in high category. © 2017 Universitas Negeri Semarang p-ISSN 2252-6617 e-ISSN 252-6232  Corresponding author: Ani Rusilowati 1 Physics Department, Faculty of Mathematics and Natural Science, Universitas Negeri Semarang E-mail: rusilowati@yahoo.com