Question

The liquid (mercury) meniscus in capillary tube will be convex if the angle of contact is

• A. greater than \(90^{\circ}\)
• B. less than \(90^{\circ}\)
• C. equal to \(90^{\circ}\)
• D. equal to \(0^{\circ}\)

Hint:

Convex meniscus = obtuse angle = non-wetting liquid; Concave meniscus = acute angle = wetting liquid.

Answer 1

The Correct Option is A

Step 1: Concept
Angle of contact determines the shape of the meniscus.

Step 2: Analysis
- Acute angle ($\theta < 90^\circ$): Concave meniscus (e.g., Water in glass).
- Obtuse angle ($\theta > 90^\circ$): Convex meniscus (e.g., Mercury in glass).

Step 3: Conclusion
For mercury, which does not wet the surface, the meniscus is convex and the angle is obtuse.
Final Answer: (A)