Absorptance

Absorptance also referred to as absorption factor is the property of a body which determines the fraction of the incident radiation or sound flux absorbed or absorbable by the body. It is defined as the ratio of the luminous or radiant flux absorbed by a body to the flux falling on it. It is usually represented by the Greek letter α (alpha). It was previously known as absorptivity. In the case of a blackbody, absorptance i.e. α = 1. Standard unit of absorptance is percent (%) or a factor between 0 and 1.