The measured contact angle is calculated for a rough, heterogeneous surface using the Wenzel and Cassie laws. The contact surface is a mixture of materials and . With sliders, you can change the fraction of component and the surface contact angles of each material ( and ). Also a slider can change the surface roughness; for a completely smooth surface, the surface roughness ratio used in the Wenzel equation is 1. The measured contact angle () is calculated and displayed above the water droplet graphic; arrows on this plot show where is measured. Surfaces with water contact angles ° have low wettability and are considered hydrophobic, whereas ° means the surface has high wettability and is considered hydrophilic. When °, complete wetting occurs.