A long glass capillary is dipped in water. It is known that water wets glass completely. The water level rises by h in the tube whose length outside water is more than h . The tube is now pushed down

Question

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

TestHub · Accepted Answer

Initially (angle of contact 0 ∘ ): h = r ρ g 2 T ​ After pushing down, the meniscus at the top adjusts its curvature: 2 h ​ = r ρ g 2 T cos θ ​ = h cos θ cos θ = 2 1 ​ ⇒ θ = 6 0 ∘

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