Reflectance is the 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 different reflectance values, which can affect how they appear to the human eye. In practical applications, reflectance is important in fields like photography, solar energy, and environmental science. For example, surfaces with high reflectance, such as snow or water, can influence local temperatures and climate patterns. Understanding reflectance helps in designing better materials and improving energy efficiency.