Correct Answer  Option 2 : 5 hr 37 min
Concept
Given,
Height of jar = 30 cm
From stokes law
We know the velocity of settling particle is
\({V_s} = \frac{{{\gamma _w} \times {d^2} \times \left( {G  1} \right)}}{{18 \times \mu }}\)
Where,
γ_{w }is the unit weight of water
d is the diameter of the particle
G is the specific gravity of the particle
μ is the viscosity of the fluid
Note: If the lighter particle from the group of particles settles at the bottom that means every particle is settled at the bottom.
Particle size (mm)

Weight (gm)

0·06

6

0·05

20

0·03

15

0·015

5

0·004

4

∴ Here diameter (d) = 0.004 mm is taken from the group
\(Time\;required\;for\;settling\;of\;all\;particle = \frac{{Height\;of\;water\;level\;in\;jar}}{{Settling\;Velocity\;}}\)
\(t = \frac{{30 \times {{10}^{  2}}}}{{14.284 \times {{10}^{  6}}}}\)
= 20215 sec
= 5.61 hr
= 5 hr 37 min