Figure 5.7 — Radiation force of a plane wave on a sphere Figure 5.7 — Radiation force of a plane wave on a sphere. Radiation force [Eq. (5.123)] produced on a sphere by a linearly polarised plane wave plotted as a function of (a) the sphere radius a and (b) the sphere size parameter kma. The medium refractive index is nm = 1.33 and the particle refractive index is np = 1.50. The vacuum wavelength is λ0 = 633 nm and the electric field amplitude is Ei = 105 V/m, corresponding to 1.8 · 107 W/m2.