Water rises to height of 20mm in capillary tube hving cross sectional area A. If the area of the cross section of the tube is made A/4, then find the rise of height water.

Explanation

`(Delta_2)/(Delta_1) = (r_2^2)/(r_1^2)`
`therefore (A/4)/A = 1/4 = (r_2^2)/(r_1^2)`
`therefore (r_2)/(r_1)` = 1/2`
`therefore (r_1)/(r_2)` =2
For capillary rise `h_1 r_1 = h_2 r_2`
`therefore h_2 = (h_1 r_1)/r_2 = 20 xx 2 = 40 mm = 4cm`