Talbot–Plateau law
the principle that if a light flickers so rapidly that it is perceived as continuous, its brightness will be determined by the ratio of the duration of the on period to the off period. Thus, the perceived brightness of the stimulus that appears continuous is actually an average of the brightness of the on and off periods. [William Henry Fox Talbot (1800–1877), British physicist; Joseph Antoine Ferdinand Plateau (1801–1883), Belgian physicist]