Question

A long glass capillary tube is dipped in water. It is known that water wets glass. The water level rises by \( h \) in the tube. The tube is now pushed down so that only a length \( h/2 \) is outside the water surface. The angle of contact at the water surface at the upper end of the tube will be

• A. \( 30^\circ \)
• B. \( 60^\circ \)
• C. \( 15^\circ \)
• D. \( 45^\circ \)

Hint:

Capillary action is influenced by the surface tension of the liquid and the angle of contact between the liquid and the tube.

Answer 1

The Correct Option is B

Step 1: Understanding capillary action.
When the tube is pushed into the water, the water rises due to capillary action. The angle of contact depends on the tube's length and the relative position of the surface. The angle at the upper end is \( 60^\circ \).

Step 2: Conclusion.
The angle of contact at the water surface is \( 60^\circ \), which corresponds to option (2).