Gold number of a lyophilic sol is such a property that:

The mass of Haemoglobin in $mg$ required to protect from coagulation of $50 \ mL$ of a gold sol on adding $5 \ mL$ of $10 \% NaCl$ solution is: (Gold number of Haemoglobin $= 0.03$)

The Tyndall effect is observed only when the following conditions are satisfied $:$
$1$. The diameter of the dispersed particles is much smaller than the wavelength of the light used.
$2$. The diameter of the dispersed particle is not much smaller than the wavelength of the light used.
$3$. The refractive indices of the dispersed phase and dispersion medium are almost similar in magnitude.
$4$. The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.

When a solution of $AgNO_3$ is added to a solution of $KI$,a negatively charged sol is formed when they are in which of the following proportions?

Point out the false statement:

Tyndall effect is observed when