Question

Two capillary tubes of same diameter are kept vertically one each in two liquids whose relative densities are 0.8 and 0.6 and surface tensions are 60 and 50 dyne/cm respectively. Ratio of heights of liquids in the two tubes $\frac{h_{1}}{h_{2}}$ is

• A. $\frac{10}{9}$
• B. $\frac{3}{10}$
• C. $\frac{10}{3}$
• D. $\frac{9}{10}$

Answer 1

Answer: (D)

$\frac{9}{10}$

Answer 2

$h = \frac{2T\cos\theta}{rdg}$ [If diameter of capillaries are same and taking value of θ same for both liquids]

∴ $\frac{h_{1}}{h_{2}} = \left( \frac{T_{1}}{T_{2}} \right)\left( \frac{d_{2}}{d_{1}} \right) = \left( \frac{60}{50} \right) \times \left( \frac{0.6}{0.8} \right) = \left( \frac{36}{40} \right) = \frac{9}{10}$.