Left: radial profiles of the degree of polarisation only for the scattered radiationof a protoplanetary disk for different values of the radial density exponent γ. Right: normalised intensity profile of re-emitted plus scattered flux. A higher value of the exponent γ corresponds to a steeper density distribution, and the intensity gradient is larger. The gradient of the intensity profile may serve as a qualitative measure for the anisotropy of the radiation field. Larger gradients lead to a higher degree of anisotropy and thus to a higher degree of polarisation.