eng Science and Education Publishing International Journal of Physics 2333-4886 2014-03-11 2 1 23 29 10.12691/ijp-2-1-5 IJP2014215 article Laith A. Najam dr_laithahmed@yahoo.com 1 Ahmed K. Mheemeed 2 Isra.a M. Hassan 2 Department of Physics, College of Science, University of Mosul, Iraq Department of Physics, College of Education, University of Mosul, Iraq In this paper, we use a narrow collimated beam of mono- energetic gamma rays emitted from the radioactive source 137Cs (662 keV) and the system of measuring gamma rays UCS-20 associated with the sodium iodide detector NaI (Tl) to determine the homogeneity of the building materials, Granite, Marble, Cement, Ceramic and Bricks. The homogeneity test was determined from the percentage difference between the transmitted intensity of gamma-rays and the linear attenuation coefficient at different positions for each sample of the material then the percentage of standard deviation was checked. http://pubs.sciepub.com/ijp/2/1/5/ijp-2-1-5.pdf gamma-ray homogeneity building materials sodium iodide detector NaI (Tl)