Definition

1. Noun:
   • The rate of flow of light energy: Luminous flux is a photometric measure of the total quantity of visible light emitted by a source per unit of time. It represents the perceived power of light, adjusted for the sensitivity of the human eye, and is measured in lumens (lm).

Usage

• Luminous flux is a key technical specification for light sources like bulbs and LEDs, indicating their total visible light output.
• It is used in physics, engineering, and lighting design to quantify and compare the brightness of light sources.
• It differs from radiant flux, which measures total electromagnetic power, as luminous flux weights the power according to a standardized model of human brightness perception.

Examples

• Noun:
  • The luminous flux of this LED bulb is 800 lumens, making it suitable for a room of this size.
  • When selecting a lamp, consider its luminous flux to ensure adequate illumination.
  • The total luminous flux from the fixture determines how bright the area will appear.

Advanced Usage

• "Luminous flux density": Also known as illuminance, this is the luminous flux incident on a surface per unit area, measured in lux (lx = lm/m²).
  • The required luminous flux density for reading is about 500 lux.

Variants and Related Words

• Luminance (n): The luminous intensity per unit area of a light source or a surface in a given direction, measured in candela per square metre (cd/m²). It relates to brightness as perceived by an observer.
• Luminous intensity (n): A measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, measured in candela (cd).
• Illuminance (n): The total luminous flux incident on a surface, per unit area.

Synonyms

• Light flux: A less common, informal synonym for luminous flux.
• (None precise): In technical contexts, it is typically referred to specifically as "luminous flux" or "flux."

Related Phrases

• Total luminous flux: Emphasizes the integrated light output over all directions from a source.
  • The product datasheet lists the total luminous flux.
• Luminous flux output: Another way to specify the light-emitting capability of a source.
  • The luminous flux output decreases as the lamp ages.

Notes

• Luminous flux is a fundamental concept in photometry, the science of measuring light as perceived by the human eye. It is crucial for applications where human vision is the primary concern, such as architectural lighting, display technology, and safety standards.

Noun

1. the rate of flow of light energy