  In general the experiments on the linear optical properties of a single-layer
two-dimensional atomic crystal are interpreted by modeling it as a homogeneous
slab with an effective thickness. Here I fit the most remarkable experiments in
graphene optics by using the Fresnel coefficients, fixing both the surface
susceptibility and the surface conductivity of graphene. It is shown that the
Fresnel coefficients and the slab model are not equivalent. Experiments
indicate that the Fresnel coefficients are able to simulate the overall
experiments here analyzed, while the slab model fails to predict absorption and
the phase of the reflected light.
