What does a foot candle measure?

• A. The amount of light that falls on a surface, such as a floor or table
• B. The brightness of ceiling lamps
• C. A power rating of lighting fixtures
• D. The color temperature of lighting

Answer: (A)

Foot-candle measures the amount of light that falls on a surface. It’s an illuminance unit, meaning it describes how much light reaches floors, tables, or other surfaces. One foot-candle equals one lumen arriving per square foot, so it’s about the light on a surface, not the brightness of the light source itself. This is different from the fixture’s power rating (watts) or the color temperature of the light (measured in kelvin), and it isn’t a measure of how bright the ceiling lamp looks from a distance. So, the best description is that foot-candle tells you how much light lands on a surface.