The units of the ç’s in eq 1 are erg/cm2 (energy per unit area),
and we have been taught and have learned to think in these terms
(energy per unit area). The units can also be expressed as dyn/
cm, and the discussion below suggests that these units (force/
length) give a more intuitive meaning. Wenzel
1 realized that
when a droplet contacts a rough surface and forms a sessile
droplet with a smooth liquid vapor interface, but rough (more
surface area) liquid solid and solid vapor interfaces, Young’s
equation (eq 1) should bemodified bymultiplying the numerator
of the right side of eq 1 by a roughness factor, r, that is the actual