Which of the following best defines a lumen?

• A. The amount of energy consumed by a light source per hour
• B. The amount of light on one square foot as produced by a candle one foot away
• C. The color temperature of the light
• D. The intensity of current in the circuit

Answer: (B)

Lumen is a measure of the total amount of visible light a source emits. In practical terms, we often relate that light to what actually reaches a surface. This option describes how much light lands on a specific surface area (one square foot) from a nearby candle, which is a way to express illumination on that surface. That link between a light source and the light arriving on a surface is what people use when they talk about how bright a space will feel, which is measured in foot-candles (lumens per square foot). So this framing connects the concept of light output to the real-world effect you experience in a space.

The other choices describe unrelated properties: energy use over time (watts or watt-hours), color temperature (measured in Kelvin), and electrical current (amperes). These are different aspects of lighting, not the amount of light emitted.