JEE MainPhysicsMechanical Properties of Fluids
Two identical capillary tubes are dipped vertically into two different liquids, X and Y . It is observed that liquid X rises in the tube by a height h , while liquid Y falls in the tube by a depth h (where h > 0 ). Identify the correct statement regarding their contact angles ( _X , _Y ) and meniscus shapes.
Options
- ALiquid X has _X > 90^ with a convex meniscus, and liquid Y has _Y < 90^ with a concave meniscus.
- BBoth liquids have < 90^ and concave meniscuses.
- CLiquid X has _X 90^ with a convex meniscus.
- DLiquid X has _X 90^ with a concave meniscus.
Correct answer
C. Liquid X has _X 90^ with a convex meniscus.
Step-by-step solution
The height of capillary rise or fall is given by h = 2S g r . For liquid X , the height is positive (capillary rise), which implies _X > 0 . Therefore, the contact angle _X is acute ( _X For liquid Y , the height is negative (capillary fall), which implies _Y 90^ ), and the meniscus is convex. Answer: Liquid X has _X 90^ with a convex meniscus.