Total flux and degree of polarization of incident unpolarized light that has been singly scattered by four different types of cloud particles, as functions of the phase angle α and the wavelength λ. Left column: total flux or phase function (single-scattering matrix element P₁₁). Right column: degree of polarization (−P₂₁/P₁₁). First row: H₂O particles with r_eff = 10 µm and υ_eff = 0.1 (belonging to the Phase 1 model planet: ‘Current Earth’). Second row: H₂O particles with r_eff = 0.5 µm and υ_eff = 0.1 (Phase 2: ‘Thin cloud Venus’). Third row: 75% H₂SO₄ particles with r_eff = 2.0 µm and υ_eff = 0.1 (Phase 3: ‘Thick cloud Venus’). Fourth row: 75% H₂SO₄ particles with r_eff = 1.05 µm and υ_eff = 0.07 (Phase 4: ‘Current Venus’).