Why is the pressure applied on the surface of the solution in osmosis?

[Sanjukta Ghosh]

Homework Statement

Why is the pressure applied on the surface of the solution?

Homework Equations

Definition: If a pure solvent and a solution is separated by a semipermeable membrane the minimum pressure applied on the surface of the solution to stop osmosis is called osmotic pressure.

The Attempt at a Solution

 

[DrClaude]

Is that a homework question (as stated), or is it a more general question?

 

[Said Ahmad]

I think it's more a general question.

Cause the surface is a boundary between two different substances.