Surface tension is the property of a fluid surface that causes it to behave like an elastic sheet. It’s the force per unit length acting perpendicular to the surface. The surface tension ($\gamma$) of a liquid is defined as the force acting per unit length along the interface between the liquid and the gas phase. The formula for surface tension is:

Where:

• $\gamma$ is the surface tension,
• $F$ is the force acting perpendicular to the surface,
• $L$ is the length of the interface over which the force is acting.