Which of the following is true for a $Fe(OH)_3$ sol?

Light scattering in colloidal particles is

Which metal sol cannot be prepared by Bredig's arc method?

Explain the coagulation of lyophilic sols and the protection of colloids.

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$ : The diameter of colloidal particles in solution should not be much smaller than the wavelength of light to show Tyndall effect.
Reason $R$ : The light scatters in all directions when the size of particles is large enough.
In the light of the above statements,choose the correct answer from the options given below:

When a few drops of dilute $HCl$ are added to a freshly prepared precipitate of ferric hydroxide,a reddish-brown colloidal solution is obtained. This phenomenon is known as .......