Studying of the optical properties of poly (vinyl alcohol) films using Aluminum sulphate as additive by measuring allowed direct transition energy gap. Baghdad Sci.J [Internet]. 2025 Feb. 25 [cited 2025 Jun. 18];8(1):103-9. Available from: https://bsj-ojs.uobaghdad.edu.iq/index.php/BSJ/article/view/1141