THE VALIDITY AND FEASIBILITY OF A HANDBOOK ON THE PROPERTIES OF LIGHT AND REFLECTIONS INTEGRATED WITH 1-SIDE HOLOGRAM LEARNING MEDIA FOR MIDDLE SCHOOL STUDENTS. SPEKTRA [Internet]. 2026 Mar. 9 [cited 2026 May 28];11(1):10-21. Available from: https://ojs.unsiq.ac.id/index.php/spektra/article/view/8841