Influence of the upper, r₊, and lower, r₋, limit of the particle radii of aligned silicates on the spectral shape of the dichroic polarisation. Shown are prolates with a/b = 2 and q = 3.5. Top: r₊ is held constant at 450 nm and polarisation spectra are computed for r₋ = 50, 80, and 200 nm that give rise to a maximum polarisation of p/τ_V = 2.1%, 1.6%, and 0.8%, respectively. Bottom: lower limit of r₋ = 100 nm and varying r₊ = 300, 450, and 600 nm that produce a maximum polarisation of p/τ_V = 1.7%, 1.4%, and 1.2%, respectively.