What unit is used to describe luminous intensity?

What unit is used to describe luminous intensity?

• A. Lux
• B. Watt
• C. Candela
• D. Joule

Answer: (C)

Luminous intensity is measured in candelas. This unit specifically quantifies the amount of light that a source emits in a particular direction, making it essential for understanding how bright a light source will appear from a given angle. The definition of a candela is based on the light emitted by a source that radiates monochromatic light at a frequency of 540 terahertz and has a radiant intensity of 1/683 watt per steradian. This direct correlation with the human perception of light makes the candela the standard unit for luminous intensity in various contexts, such as lighting design, visual ergonomics, and safety regulations. Other units listed, like lux and watt, serve different purposes; lux measures illuminance (light per unit area), while watt denotes power as an energy unit. Joules, on the other hand, refer to energy as well. Understanding these differences helps clarify the specific function that the candela serves in the field of photometry.

Luminous intensity is measured in candelas. This unit specifically quantifies the amount of light that a source emits in a particular direction, making it essential for understanding how bright a light source will appear from a given angle. The definition of a candela is based on the light emitted by a source that radiates monochromatic light at a frequency of 540 terahertz and has a radiant intensity of 1/683 watt per steradian.

This direct correlation with the human perception of light makes the candela the standard unit for luminous intensity in various contexts, such as lighting design, visual ergonomics, and safety regulations.

Other units listed, like lux and watt, serve different purposes; lux measures illuminance (light per unit area), while watt denotes power as an energy unit. Joules, on the other hand, refer to energy as well. Understanding these differences helps clarify the specific function that the candela serves in the field of photometry.