What index measures how faithfully a light source renders colors?

• A. Luminous Flux
• B. Color Rendering Index
• C. Illuminance
• D. Luminance

Answer: (B)

Color Rendering Index measures how faithfully a light source renders colors, by comparing how colors look under that light to how they look under a reference illuminant. The index ranges up to 100, with higher values indicating more accurate color appearance; a perfect match to the reference light is 100. This concept is useful because it tells you how natural colors will appear in real life under a given lamp, which matters for tasks like color matching or any setting where color perception is important. The other terms describe different aspects of light: luminous flux is the total amount of light emitted, illuminance is the light on a surface, and luminance is the perceived brightness of a surface.