Efficiency factors as a function of grain size for an amC particle computed with full Mie theory (lines dashed red: absorption; dash-dotted blue: scattering; black: radiative pressure) and in the SPL approximation (absorption, plus signs). Top panel: values at a wavelength of 0.54 μm (V band). Bottom panel: values at a wavelength of 2.1 μm (K band; see text for details). While scattering is negligible in the SPL, it contributes significantly to the radiation pressure for particles with sizes that are comparable to the wavelength.