Question

Water rises to a height of `10 cm` in a capillary tube and mercury falls to a depth of `3.42 cm` in the same capillary tube. If the density of mercury is `13.6 g//c.c.` and the angles of contact for mercury and for water are `135^@` and `0^@`, respectively, the ratio of surface tension for water and mercury is
A. `1 : 0.15 `
B. `1 : 3`
C. `1 : 6.5`
D. `1.5 : 1`

Answer 1

`h=(2Tcostheta)/(rrhog)`
or `s=(hrrhog)/(2costheta)`
or `S prop(hrho)/(costheta)`
`(S_(w))/(S_(Hg))=(h_(1))/(h_(2))xx(costheta)/(costheta_(1))xx(rho_(1))/(rho_(2))`
Putting the values, we obtain `1 : 6.5`