Question

What term is used to describe how to measure the reflectivity of a surface?

Answer 1

The term used to describe how to measure how reflective the surface is, is the surface albedo. Surface albedo represents the ratio of irradiance reflected to the irradiance recieved by a surface. The proportion reflected is not only determined by properties of the surface itself, but also by the spectral and angular distribution of a solar radiation reaching the Earth's surface.