$A$ milk-water mixture,when viewed by reflected light,appears in which colour?

Explain what is observed:
$(i)$ When a beam of light is passed through a colloidal sol.
$(ii)$ An electrolyte,$NaCl$,is added to hydrated ferric oxide sol.
$(iii)$ Electric current is passed through a colloidal sol.

The gold numbers of gelatin, haemoglobin and sodium acetate are $5 \times 10^{-3}$, $5 \times 10^{-2}$ and $7 \times 10^{-1}$, respectively. The protective actions will be in the order

Which among the following ionic species has the least precipitating power?

Identify a zero dimensional nano structure from the following.

Soap essentially forms a colloidal solution in water and removes the greasy matter by: