22 August 2006
Visibility the quality or state of being perceivable by the eye.
Volt the difference in electrical potential between two points in a circuit.
Watt the unit of power (rate of doing work). In electrical calculation, one watt is the
poser produced by a current of one ampere across a potential difference of one volt.
Workplane the plane on which a visual task is usually done, and on which the
illuminance is specified and measured.