NCIDQ Interior Design Professional Exam (IDPX) Practice Exam

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What is the term used to measure the intensity of a light source in directional luminaires?

  1. Candlepower

  2. Lumen distribution chart

  3. Color rendering index chart

  4. Footcandle distribution chart

The correct answer is: Candlepower

The term used to measure the intensity of a light source in directional luminaires is "candlepower." Candlepower refers to the amount of light emitted by a light source in a specific direction and is an important metric when evaluating how effectively a luminaire can direct light in a desired direction. It is particularly relevant for directional lighting, such as spotlights or floodlights, where control over the intensity and direction of light is critical for both aesthetic and functional purposes. In contrast, the other terms have different meanings and uses. A lumen distribution chart provides information on how light spreads across a given area but does not focus on the intensity in a specific direction. The color rendering index chart measures how accurately a light source displays colors in comparison to a natural light source, which is not related to the intensity of light emitted in a particular direction. Finally, a footcandle distribution chart indicates the illumination level (in footcandles) at various points in a space, which is relevant for overall light intensity but does not specifically measure the intensity of light from a single luminaire in a direction. Therefore, candlepower is the correct term for the specific context of measuring intensity in directional luminaires.