Comment on “Comprehensive physical studies on nanostructured Zn-doped CdSe thin films [Journal of Alloys and Compounds 789 (2019) 108–118]; Structure, optical and transport properties of Mg-doped ZnMn2O4 [Journal of Alloys and Compounds 655 (2016) 188–197]”

In the literature a widely spread equation to correlate between the optical (σoptic) and electrical (σelec) conductivities in the form of (σelec=2λσoptα). Unfortunately, the tow sides of this equation have different dimensions i.e this equation is incorrect and the work by this equation must be stopped. The calculation of electrical/optical conductivity should be limited to the correct forms only deduced from the correct solution of Maxwell's equations.