What is the term for the amount of light that will illuminate a surface 1 foot from the source?

The correct term for the amount of light that will illuminate a surface 1 foot from the source is foot candle. A foot candle measures the amount of light falling on a surface from a light source, specifically accounting for the distance of one foot from that source. This measurement is commonly used in lighting design and refers to the illumination level on a surface, making it a relevant unit for assessing light intensity in practical applications.

Candlepower, while similar, refers to the intensity of light emitted from a source in a particular direction and does not provide information about the illumination on a surface at a specific distance. Therefore, it does not accurately convey the overall light exposure at a measurement point like a foot candle does.

Lumen refers to the total quantity of visible light emitted by a source, which is a broader measure and does not correlate directly to the intensity of light at a specific distance from the source.

Ballast is a device used in lighting to regulate the current to the light source but is not a measurement of light intensity.

In summary, foot candle is the most precise term for the illumination on a surface at a distance of one foot from a light source, which is why it is the correct answer.