We present a simple model to study the effects of displacing a single atomic monolayer on the linear optical properties of a material. As an example, we calculate the change in reflectance of a Si(111)(1 × 1):H slab after disordering successively deeper atomic layers. We find that the reflectance varies significantly at photon energies above 2.0 eV, and that the disordered slab produces a larger reflectance than the relaxed slab. The results also show a quantitative difference in the contribution from the odd and even atomic layers to the calculated reflectance. This simplified model is a first approach; also, it can be extended to consider more realistic systems that can be probed by techniques such as coherent acoustic phonon (CAP) spectroscopy, and can also be applied to two‐dimensional materials.