A question now arises. Can the fluid really come out of the capillary? (If so, laws of thermodynamics will be violated!)
Assume that the fluid flows out of the capillary. In that case, the shape of meniscus will change from bulging inward to bulging outwards. But this will not be energetically favorable. So, the fluid will not flow out and thermodynamic laws are not violated..

If is the atmospheric pressure at the inlet, then

We can see that penetration can occur even if . But for , has to be greater than for penetration to occur.