Definition

Noun: - The luminous intensity of a light source in a given direction, measured in candelas (cd). This is a specific photometric quantity in physics that describes the power of light emitted per unit solid angle. It is a measure of the wavelength-weighted power emitted by a light source, as perceived by the human eye.

Usage

• This term is used in technical, scientific, and engineering contexts, particularly in physics, optics, photography, and lighting design.
• It quantifies the brightness of a point source of light as it appears to an observer.
• Example:
• Example:

Advanced Usage

• "Light intensity" is a foundational concept in radiometry and photometry. It is distinct from related terms like illuminance (light falling on a surface, measured in lux) and luminance (light emitted or reflected from a surface, measured in cd/m²).
• In practical applications, controlling light intensity is crucial for tasks such as setting exposure in photography, designing stage lighting, and ensuring proper illumination in workplaces.

Variants and Related Words

• Luminous Intensity: The formal, equivalent scientific term. "Light intensity" is often used as a more general synonym.
• Intensity (of light): A more general phrase where "intensity" refers to the strength or brightness of light, though it can be less precise.
• Candela (cd): The SI base unit for measuring luminous intensity.
• Photometry: The science of the measurement of light, in terms of its perceived brightness to the human eye.

Synonyms

• Luminous intensity (technical synonym)
• Candlepower (an older, non-SI unit of measurement, roughly equivalent to the candela)

Related Phrases and Concepts

• Inverse-square law: A physical law stating that the intensity of light (illuminance) from a point source is inversely proportional to the square of the distance from the source. While this law directly governs illuminance, it is fundamentally linked to the source's luminous intensity.
• Light output: A more general, non-technical term often used to describe the total perceived brightness of a lamp or fixture.

Noun

1. luminous intensity measured in candelas