Which unit is used to describe light intensity in this context?

• A. Lux
• B. Foot-candles
• C. Lumens
• D. Candela

Answer: (B)

Illuminance—the amount of light landing on a surface—is what this question is asking about. Foot-candles measure that illuminance in imperial units, as lumens per square foot. This makes them the natural choice for describing how bright a work area or enclosure appears in many lab settings.

Candela relates to luminous intensity of a light source in a direction, not how bright a surface gets. Lumens quantify total light emitted by the source, not what actually reaches a specific area. Lux is the metric counterpart of illuminance (lumens per square meter). If you ever map between systems, 1 foot-candle is about 10.764 lux, and 1 lux is about 0.0929 foot-candles.