1 De part ment of Elec tron ics and Com mu ni ca tions, Fac ulty of En gi neer ing, Yalova Uni ver sity, Yalova, Tur key 2 De part ment of Phys ics, Fac ulty of Sci ence, Ataturk Uni ver sity, Erzurum, Tur key Sci en tific pa per The ef fec tive atomic num ber (Z eff ) of Si x Pb 0.7-x (Fe 2 O 3 ) 0.3 ter nary al loys was ob tained for photons. Ray leigh to Compton scat ter ing ra tio (R/C) has been de ter mined to ob tain the Z eff of Si x Pb 0.7-x (Fe 2 O 3 ) 0.3 ter nary al loys of vary ing Si and Pb (10 %-60 %) con tent for scat ter ing of 59.54 keV g-rays at an an gle of 130°. The the o ret i cal R/C ra tios of el e ments were plot ted as a func tion of the atomic num ber and fit ted to a poly no mial equa tion. Ex per i men tal R/C val ues of al loys were then used to ob tain Z eff us ing this fit equa tion. Also, Z eff val ues of these al loys were de ter mined for the first time by in ter po lat ing the R/C of the ma te rial us ing the R/C data of ad ja cent el e ments in be tween the R/C of the al loy lies.The agree ment be tween the in ter pola tion method and the fit equa tion was quite sat is fac tory. The ob tained Z eff for pho ton scatter ing were then com pared to the Z eff for to tal pho ton at ten u a tion ob tained us ing the Auto-Z eff pro gram. Sig nif i cant vari a tions were ob served be tween the Z eff for scat ter ing and the to tal at ten u a tion of gamma rays.