Define 'reflectance' in the context of laser processing.

Reflectance refers to the ability of a material to reflect laser light. This property is crucial in laser processing applications, as the degree to which a surface can reflect laser energy affects the efficiency of the laser operation. For example, materials with high reflectivity might scatter or reflect a significant portion of the laser beam rather than absorbing it, influencing the outcomes of cutting, welding, or engraving processes. Understanding a material's reflectance is essential for selecting the right laser settings and ensuring optimal results in various applications. In contrast, the other options focus on attributes related to absorption, transmission, and refraction, which are separate phenomena and do not define reflectance.