Correct Answer - Option 3 : 20 cm
Concept:
Height of capillary rise is given by:
\(h = \frac{{2\sigma \cos \theta }}{{\rho gr}}\)
where,
σ = surface tension of the fluid.
θ = angle of contact between the glass tube and the fluid
ρ = density of the fluid
r = radius of the glass tube (size)
Calculation:
Given:
Size r1 = 4 mm, h1 = 10 cm
Size r2 = 2 mm, h2 = ?
Height of capillary rise is given by:
\(h = \frac{{2\sigma \cos \theta }}{{\rho gr}}\)
\(∴ h\propto\frac{1}{r}\)
h1 × r1 = h2 × r2
4 × 10 = h2 × 2
∴ h2 = 20 cm
