candela

/kən'dəlɑ:/

Thân thiện

The scientist measures the luminous intensity of the light source in candelas.

Definition

1. Noun:
   • The base unit of luminous intensity in the International System of Units (SI): A "candela" is the scientific unit that measures the brightness of a light source as perceived by the human eye. It is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of a specific frequency.

Usage

• The "candela" is used in physics, engineering, and lighting design to quantify how bright a light appears.
• It is one of the seven base SI units.
• It is used to specify the intensity of light sources like LEDs, light bulbs, and lasers.

Examples

• Noun:
  • A standard candle emits light with an intensity of about one candela.
  • The laser pointer has an output of 5 millicandelas.
  • The new regulations specify the minimum luminous intensity in candelas for vehicle headlights.

Advanced Usage

• "Candela per square meter (cd/m²)": This is the derived SI unit for luminance, which describes the brightness of a surface that emits or reflects light.
  • The luminance of a typical computer screen is around 200 to 300 candelas per square meter.

Variants and Related Words

• Lumen (n): A unit of luminous flux, measuring the total amount of visible light emitted by a source. Related to the candela.
• Lux (n): A unit of illuminance, measuring the amount of light falling on a surface. One lux is equal to one lumen per square meter.

Synonyms

• Candlepower (n): An older, non-SI unit of luminous intensity that is approximately equal to one candela. (Note: This is a near-synonym from an older system of measurement.)

Notes on Meaning

• The "candela" measures , which is the power of light weighted by the sensitivity of the human eye. It is not a measure of total light output (lumen) or the light falling on a surface (lux).
• Its formal definition is based on the properties of a theoretical "black body" radiator at a specific temperature.

Học thuật

Noun

1. the basic unit of luminous intensity adopted under the Systeme International d'Unites; equal to 1/60 of the luminous intensity per square centimeter of a black body radiating at the temperature of 2,046 degrees Kelvin

Từ đồng nghĩa

• candle
• cd
• standard candle