The ___________ indicates how much of the light falling on a surface is reflected*EfficacyIlluminanceReflectance FactorBrightness

The correct answer is "Reflectance Factor."

Explanation:

Reflectance Factor is a critical concept in optics and lighting design. It describes a surface's ability to reflect light relative to the amount of light that strikes it. This is significant in various applications such as architectural lighting, photography, and even in understanding ecological light interactions.

In practical terms, the Reflectance Factor is expressed as a ratio or percentage. For instance, if a surface reflects 70% of the light that hits it, its Reflectance Factor would be 0.7 or 70%. This factor helps in determining the overall brightness and energy efficiency of a space, as well as in designing systems that adequately illuminate an environment based on the characteristics of different surfaces. Understanding this factor is vital for accurate lighting calculations and ensuring optimal lighting conditions in different settings.