Magneto-optical and optical spectroscopies have been applied to study a wedge-shaped Fe/Zr multilayer with Fe sublayers thickness varying from about 4.1 to 1.4 nm and with Zr sublayers of thickness kept nearly constant (d(Zr) = 1.8-1.6 nm), The experimental data are discussed in the framework of an electromagnetic wave model for a multilayered structure. For d(Fe) > 2 nm computer simulations of the spectral dependencies of equatorial magneto-optical Kerr effect are well described by this approach, while for d(Fe) less than or equal to 2 nm, a severe discrepancy between modelled and experimental spectra are observed if we employ bulk magneto-optical data of Fe and bulk optical constants of Fe and Zr. This may serve as an additional support of a crystalline-to-amorphous transition in Fe sublayers below a critical thickness of d approximate to 2 nm.