The angle of contact of mercury with soda lime glass is `140^(@)`. A capillary tube of radius 1.0 mm is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside?
Surface tension of mercury `=0.465Nm^(-1)`
Density of mercury `=13.6xx10^(3)kgm^(-3)`

Explanation

Capillary descent, `" " h = (2 T cos theta)/(r rho g) = (2 xx (0.465 Nm^(-1))(cos 140^@))/((2 xx 10^(-3) m)(13.6 xx 10^3)(9.8 m s^(-2)))`
`implies " " h = -6.89 xx 10^(-4) m`
Where, negative sign indicates that there is fall of mercury (mercury is depressed) in glass tube.