This research focuses on electromagnetic waves propagation when the incident waves interact with different materials. The finite difference time domain (FDTD) technique is utilized for studying the propagation of the electromagnetic waves when the wave interacted with obstacles such as a dielectric and perfect electric conductor (PEC) inserted in the domain. The electromagnetic problems could be solved by discretizing the differential form of Maxwell’s curl equations. The propagations of electromagnetic waves in a dielectric material in a one dimension (1D) demonstrated that the symmetry of distributions appeared when the results compared as the sources assigned to different electric field node. Moreover, we simulated the problems in two dimensions (2D) for calculating the electric and magnetic field components as pixel by pixel in the x-y plane. In this case, two different types of obstacles utilized to compare the results. The results illustrated that the waves totally reflected back into the space and the waves propagated in the opposite direction compared with the incident signal once the PEC inserted. There is no field appeared inside the PEC obstacle whereas utilizing a dielectric obstacle, the fields generated inside a dielectric and everywhere nearby the obstacle. The results compared between the calculations when the dielectric slab and PEC slab placed in the same area. The first simulation showed that part of signal transmitted into next area whereas the second simulation result illustrated that the field reflected, there is no signal appeared and produced in the next area after the slab. The results have explained that the electric and magnetic fields reflected back and updated after the obstacles in the space when dielectric slab in the same area of the PEC slab.