Physics - Fluid Question with Solution | TestHub

The shape of the liquid meniscus in a capillary tube depends on the angle of contact between the liquid and the solid surface.

If the angle of contact is acute (less than $90^{\circ }$), the liquid wets the solid surface and the meniscus is concave.

If the angle of contact is obtuse (greater than $90^{\circ }$), the liquid does not wet the solid surface and the meniscus is convex.

For mercury in a glass capillary tube, the angle of contact is obtuse (approximately $140^{\circ }$), which is greater than $90^{\circ }$. Therefore, its meniscus is convex.

Answer: greater than $90^{\circ }$