I was going through the derivation of height of a liquid in a capillary tube when I came up with a doubt...although its a very basic doubt and you may laugh at it...but please help me...I was thinking that when derived the expression that H=2T/rdg where T is the surface tension,d is the density of the liquid in the tube,r is the radius of the meniscus,g is the acceleration due to gravity and H is the height of the liquid...we said that the pressure should be same at the same level in a liquid...this I understood...but when we compared the pressure at 1) the end of the capillary tube which is dipped in liquid and 2) another point in the beaker at the same horizontal level...but at that other point shouldn't the surface be curved so the pressure would be either 2T/r more or 2T/r less than the atmospheric pressure...What I really mean to ask is that why in a capillary tube (suppose the liquid is water) the water surface is curved and makes a certain contact angle with the tube whereas in a beaker which is just like a capillary tube with a BIG radius the water level is plain (or flat) and the contact angle 90 degree?


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