A batch settling experiment is performed in a long column using a dilute dispersion containing equal number of particles of type $A$ and type $B$ in water (density $1000 \text{ kg m}^{-3}$) at room temperature.
Type $A$ are spherical particles of diameter $30\: \mu m$ and density $1100 \text{ kg m}^{-3}$.
Type $B$ are spherical particles of diameter $10\: \mu m$ and density $1900 \text{ kg m}^{-3}$.
Assuming that Stokes’ law is valid throughout the duration of the experiment, the settled bed would
- consist of a homogeneous mixture of type $A$ and type $B$ particles
- consists of type $B$ particles only
- be completely segregated with type $B$ particles on top of type $A$ particles
- be completely segregated with type $A$ particles on top of type $B$ particles