What unit measures illumination in terms of foot candles?

The correct response measures illumination in foot candles by quantifying the amount of light that reaches a surface area of one square foot from a light source. A foot candle is defined as the illumination produced by a light source that emits one lumen of light uniformly across a one-foot square area. Therefore, saying "amount of light per square foot" accurately reflects the measurement of illumination.

In this context, other options may refer to different units or concepts that do not directly describe the illumination intensity. For instance, "meter squared" and "foot squared" pertain to units of area, which don't specifically quantify light intensity or distribution. "Area per light source" is ambiguous and does not clearly define how illumination is measured with respect to the amount of light hitting a surface. Thus, the correct choice effectively captures the essence of what a foot candle represents in terms of light measurement.