1. Capillary rise formula

For a liquid rising in a capillary tube,

$h = \frac{2T\cos\theta}{\rho g r}$

where:

• $T$ = surface tension,
• $\theta$ = angle of contact,
• $\rho$ = density of liquid,
• $r$ = radius of capillary tube.

Since both tubes are identical, $r$ is same.

2. For water in tube A

For clean water in a glass capillary:

• angle of contact is nearly $0^\circ$,
• so $\cos\theta \approx 1$,
• surface tension is relatively high.

Thus,

$h_A = \frac{2T_w}{\rho_w g r}$

Water rises appreciably.

3. For soap solution in tube B

Adding soap decreases the surface tension of water significantly. Also, soap solution still wets glass, so $\theta$ remains close to $0^\circ$ and $\cos\theta \approx 1$.

Thus,

$h_B = \frac{2T_s}{\rho_s g r}$

with

$T_s < T_w$

and densities are nearly comparable, so the dominant effect is reduced surface tension. Therefore,

$h_B < h_A$

So the liquid column rises in both tubes, but the rise in soap solution is less than that in pure water.

4. Relative nature of columns

Hence:

• In both capillaries, liquid rises above the outside level.
• The rise in tube A (water) is greater than in tube B (soap solution).

So the correct diagram must show:

$h_A > h_B > 0$

5. Comparison with stored answer

The stored correct answer is C. This matches the physical conclusion that water rises more than soap solution in identical capillary tubes.