Question

The surface of water in contact with glass wall is
A. Plane
B. Concave
C. Convex
D. Both B and C

Answer 1

This can be solved by analyzing this statement under the capillary action of a glass tube when placed in liquid like water. Capillary action occurs because water is sticky in nature due to which the water modules get attracted to the glass and stick to it.

Complete answer:
When the lower end of the glass wall is placed in the surface of liquid like water then a concave meniscus is formed. This occurs due to the adhesion nature of the water that the water molecules get attracted to the glass wall which pill the liquid column along until there is a sufficient mass of liquid for gravitational forces to overcome these intermolecular forces.

Whenever we observe capillary action then amg;le of water with glass wall in it produces an acute angle with it is also another reason we observe a concave meniscus. This Concave meniscus is also due to surface tension as to decrease surface area to volume ratio.Examples of capillary action:
-Water moving up in straw or glass tube against gravity
-Water moving through the towel against gravity.
-Uptake of water on paper.

Hence, the correct answer is option B.

Note: There are other various reasons for this capillary action. Here according to the condition this capillary action produces a concave meniscus on the surface of the glass wall. Remember that the momentum of water due to capillary action is due to the force of adhesion, cohesion and surface tension.