Moreover, the above derivation assumed an electron confined in the -direction, which is a relevant experimental situation — found in two-dimensional electron gases, for instance. Still, this assumption is not essential for the results. If electrons are free to move along the direction, the wave function acquires an additional multiplicative term exp(); the energy corresponding to this free motion, , is added to the discussed. This term then fills in the separation in energy of the different Landau levels, blurring the effect of the quantization. Nevertheless, the motion in the --plane, perpendicular to the magnetic field, is still quantized.