A lumen is the

A lumen is the

• A. Amount of light on a surface created by a candle placed at one foot
• B. Amount of light on one square foot of surface created by a candle one foot away
• C. Power consumed per hour by a light source
• D. Brightness level of a bulb at maximum output

Answer: (B)

Lumen is the total amount of visible light that a source emits per unit time, a measure of luminous flux. Thinking concretely, describing how much light lands on a specific surface at a given distance ties that flux to a measurable quantity. If a light source (like a candle) is one foot from a surface that is exactly one square foot in area, the total light reaching that surface corresponds to the lumen value. That is why this description fits lumen: it names the total light arriving on a defined surface. The other ideas describe different things: power consumption over time is energy use (not light output), brightness is a subjective perception, and talking about light on a surface without fixing the area or distinguishing flux versus intensity can mix concepts like illuminance and flux.

Lumen is the total amount of visible light that a source emits per unit time, a measure of luminous flux. Thinking concretely, describing how much light lands on a specific surface at a given distance ties that flux to a measurable quantity. If a light source (like a candle) is one foot from a surface that is exactly one square foot in area, the total light reaching that surface corresponds to the lumen value. That is why this description fits lumen: it names the total light arriving on a defined surface.

The other ideas describe different things: power consumption over time is energy use (not light output), brightness is a subjective perception, and talking about light on a surface without fixing the area or distinguishing flux versus intensity can mix concepts like illuminance and flux.