where the L j 's denote the appropriate doublet/triplet of depolarization factors which is governed by the ratios between the axis of the ellipse/ellipsoid. For example: in the case of a circle ( L 1 = 1 / 2 , L 2 = 1 / 2 ) and in the case of a sphere ( L 1 = 1 / 3 , L 2 = 1 / 3 , L 3 = 1 / 3 ). (The sum over the L j 's is unity.)