Reflectance is a measure of how much light or other electromagnetic radiation is reflected by a surface compared to the amount that hits it. It is usually expressed as a percentage, indicating the proportion of incoming light that is bounced back. Different materials have varying reflectance properties; for example, a mirror has high reflectance, while a black surface has low reflectance. In scientific terms, reflectance can be influenced by factors such as surface texture, color, and angle of incidence. It plays a crucial role in fields like optics, photography, and remote sensing, where understanding how light interacts with surfaces is essential for accurate measurements and imaging.