કેશનળીની અંદરની સપાટી પર મીણ લગાવીને તેને પાણીમાં દુબડેલ છે.મીણ લગાવ્યા પહેલા કેશનળી માટે સંપર્કકોણ \(\theta \) અને પાણીની ઊંચાઈ \(h\) હોય તો મીણ લગાવ્યા પછી તેમાં થતો ફેરફાર ...

A \(\theta \) વધે અને \(h\) પણ વધે
B \(\theta \) ઘટે અને \(h\) પણ ઘટે
C \(\theta \) વધે અને \(h\) ઘટે
D \(\theta \) ઘટે અને \(h\) વધે

Verified Solution

Answer & Solution

Correct Answer

(C) \(\theta \) વધે અને \(h\) ઘટે

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 \({T_{SA}} < {T_{SL}}\cos \theta \,is\,negative\,i.e.,\) \({90^ \circ } < \theta < {180^ \circ }\) \(i.e.,\,angle\,of\,contact\,\theta \,increases\)…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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