Which light measurement considers the area illuminated per unit?

The correct answer is footcandle because this measurement specifically refers to the amount of light received on a surface area from a light source. It is defined as one lumen per square foot, effectively quantifying how much light illuminates a specific area. This is particularly useful in assessing the brightness of environments and ensuring adequate lighting levels for tasks.

In contrast, watt is a measurement of electrical power consumption and does not relate to light output or illumination. Lumen measures the total quantity of visible light emitted by a source but does not take area into account. Candela measures luminous intensity in a particular direction and also does not factor in the area illuminated. Therefore, footcandle is the most relevant measure when discussing light intensity with respect to a specific area being illuminated.