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JEE Mains · Physics · STD 11 - 9.2 surface tension
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 angle of contact \(\theta \) and the height \(h\) upto which water rises change. These changes are
- 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
Answer & Solution
Correct Answer
(C) \(\theta \) increases and \(h\) decreases
Step-by-step Solution
Detailed explanation
Angle of contact \(\theta \) \(\cos \theta = \frac{{{T_{SA}} - {T_{SL}}}}{{{T_{LA}}}}\) when water is on a waxy or oily surface \({T_{SA}} < {T_{SL}}\cos \theta \,is\,negative\,i.e.,\) \({90^ \circ } < \theta < {180^ \circ }\) \(i.e.,\,angle\,of\,contact\,\theta \,increases\)…
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