question_answer

Wax is coated on the inner wall of a capillary tube and the tube is then dipped in water. Then, compared to the unwaxed capillary, the angel of contact \[\theta \] and the height h up to which water rises change. These changes are:                                                                                                                                                [JEE ONLINE 23-04-2013]

A)  \[\theta \]increases and h also increases

B)       \[\theta \] decreases and h also decreases

C)       \[\theta \] increases and h decreases

D)  \[\theta \] decreases and h increases

Correct Answer: C

Solution :

[c] Angle of contact when water is on a waxy or oily surface is negative i.e.,i.e., angle of contact increases And for  liquid level in capillary tube fall. i.e., h decreases