illuminance

/i'lju:minəns/
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illuminance

A student measures the illuminance on her desk with a light meter.

Definition
  1. Noun:
    • The luminous flux incident on a unit area: In physics, illuminance is the measure of the amount of light falling onto or illuminating a surface. It quantifies how much luminous power is received per unit area.
Usage
  • Illuminance is a technical term used primarily in physics, engineering, photography, and lighting design. It describes the intensity of light as it strikes a surface. The standard unit of measurement is the lux (lx), which is equal to one lumen per square meter.
Examples
  • Noun:
    • The recommended illuminance for reading is about 500 lux.
    • We measured the illuminance on the workbench to ensure it met safety standards.
    • The illuminance from the full moon is much lower than that from direct sunlight.
Advanced Usage

  • "Illuminance level": A specific quantity of illuminance, often referenced in standards or guidelines.

    • The building code specifies a minimum illuminance level for emergency exits.

  • "Illuminance meter": A device (also called a lux meter) used to measure illuminance.

    • The photographer used an illuminance meter to check the light in the studio.
Variants and Related Words

  • Illuminant (n): A source of light.

    • The sun is a natural illuminant.

  • Illumination (n): The act of illuminating or the state of being illuminated; also used more generally for lighting.

    • The room's illumination was provided by a single lamp. (Note: This is a broader term than the specific, measured quantity of "illuminance").

  • Luminous flux (n): The measure of the perceived power of light, in lumens. Illuminance is the luminous flux per unit area.

Synonyms
  • Light level: A less technical term for illuminance.
  • Irradiance (n): A related but distinct concept; it is the power of electromagnetic radiation (including non-visible light like UV) incident per unit area, measured in watts per square meter.
Notes
  • Illuminance is distinct from luminance. Luminance describes the amount of light or a surface in a given direction (its brightness to an observer), while illuminance describes the light a surface.
  • It is a key parameter in designing lighting systems for homes, offices, streets, and photographic sets to ensure adequate and comfortable visibility.
illuminance

A student measures the illuminance on her desk with a light meter.

Noun
  1. the luminous flux incident on a unit area

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