luminous intensity unit
Noun: A luminous intensity unit is a standard, quantitative measure used to express the luminous intensity of a light source. Luminous intensity is the power of light emitted by a source in a particular direction, weighted by the sensitivity of the human eye to different wavelengths of light.
This term is a technical, compound noun used in the fields of physics, engineering, and photometry. It refers to the specific unit of measurement itself, not the quantity being measured. - The candela is the base SI (International System of Units) luminous intensity unit. - When calibrating a light meter, you must ensure it is set to the correct luminous intensity unit.
- Defining Constants: Since 2019, the candela is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of a specific frequency.
- Radiometric vs. Photometric Units: A luminous intensity unit is a photometric unit, meaning it accounts for human visual perception, unlike a radiometric unit (e.g., watts per steradian) which measures raw physical power.
- Candela (cd): The SI base unit of luminous intensity.
- Candlepower: An older unit of luminous intensity, largely superseded by the candela.
- Lumen (lm): A unit of luminous flux, which is related to but distinct from luminous intensity. It is the total perceived power of light.
- Photometric Units: The broader category of measurement units for light as perceived by the human eye, which includes the luminous intensity unit.
- Unit of luminous intensity (formal equivalent)
- Photometric intensity unit (more specific to the field)
This term has a single, precise technical meaning. It does not have idiomatic or figurative uses. It is always used as a compound noun to specify the type of unit (e.g., "candela," "candlepower") rather than a specific numerical value.
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a measure of luminous intensity
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