Mahmoud Hassan Osman Fadl, Mubarak Dirar Abd-Alla, Fatma Osman Mahmoud Mohamed, Faiz M. B. Elshafia and HassabAlla M.A.Mahmoud 2022. The effect of changing the nano size on the absorption coefficient and the energy gap of crushed Na Cl samples. Eurasian Journal of Physics,Chemistry and Mathematics. 7, (Jun. 2022), 1–13.