Q 11-09-027NEETJEE MainEasy
When a glass capillary is dipped in mercury, the mercury level in the tube
Answer: (A) falls below the outside level, because the contact angle is obtuse
Mercury does not wet glass: the contact angle is about $140^\circ$, so $\cos\theta < 0$ and $h = \dfrac{2T\cos\theta}{\rho g r}$ is negative. The level is depressed and the meniscus is convex.
Solution by Sreeraj P, M.Sc Physics