Consider the rectangular sheet formed by bringing substance$-$A and substance$-$B

together. Contact angle of water on substance$-$A is $60.$ Contact angle of water on

substance$-$B is $120.$ Interfacial energy of $A-B=40m\frac{J}{m^2}*{}_{\text{w}\text{a}\text{t}\text{e}\text{r}}=73m\frac{J}{m^2}.$

${}_A=50m\frac{J}{m^2}*{}_B=20m\frac{J}{m^2}.$

A$)$ Will substance$-$A and substance$-$B detach in water?

B$)$ Draw the water contact angles appropriately and qualitatively explain what

will happen when we put the rectangular sheet on top of water as shown on the

left.

C$)$ Consider $3$ different capillary tubes all having radius $r=0\mathrm{.}1mm$ : i$)$ made of

material $A,$ ii$)$ made of material $B,$ iii$)$ made of $A-B$ composite $(f_A=0\mathrm{.}50).$

The tubes are immersed in water.

Draw $($qualitatively$)$ the shape of the meniscus and the height of the water $($with

respect to water surface out of the tube$)$ in each tube. Calculate the height in each

tube.