Microwave heating has been established in industry for many years. The temperature distribution within irradiated materials is obtained by determining the electric field distribution. For this reason, modelling the geometry under the plane wave illumination is useful. To determine the temperature distribution, the transmission line analogy for plane wave propagation and reflection for normal incidence angle is used. The heating pattern in a multilayered slab material exposed to a uniform plane wave is obtained. The lossy dielectric object is modelled as an infinitive number of cascaded transmission lines terminated with a metal plate and the inner electric field is calculated.