Mass opacity change in the case of fluffy dust growth. Each line shows the mass opacity in the cases of different radii and filling factors, which correspond to open circles in Fig. 9. The dust properties of the lines are as follows: red: a = 0.1 μm, and af = 0.1 μm; green: a = 10 μm, and af = 0.1 μm; blue: a = 1 mm, and af = 0.1 μm; magenta: a = 12.6 cm, and af = 10 μm; brown: a = 11.2 m, and af = 1 mm; purple: a = 359 m, and af = 10 cm.