question_answer

A vertical capillary tube with inside diameter 0.5mm is submerged into water so that the length of its part protruding over the surface of water is equal to 2.5mm. Find the radius of curvature of the meniscus.    

A) 0.3mm

B) 0.6mm

C) 0.9mm

D) 1.2mm

Correct Answer: B

Solution :

[b] Let the liquid rise to a height h. \[T=\frac{h\rho rg}{2}\] \[\therefore \,\,hr=\frac{2T}{\rho g}\] If the tube is of height \[{{h}_{1}}<h\] \[{{h}_{1}}{{r}_{1}}=hr=\frac{2T}{\rho g}\] \[\therefore \,\,\,\eta =\frac{2T}{{{h}_{1}}\rho g}=\frac{2\times 0.073}{\frac{25}{1000}\times 1000\times 9.8}\{25mm=\frac{25}{1000}m\}\]\[=\frac{2\times 0.073}{9.8\times 25}=0.0006m=0.6mm\]