In region 3 of a light adaptation curve, which law describes a slope of 1?

In region 3 of a light adaptation curve, a slope of 1 is characterized by Weber's Law. This law explains the relationship between stimulus intensity and perception. Specifically, it states that the ratio of change in stimulus intensity to the initial intensity is a constant; this implies that as light intensity increases, the perceived brightness increases linearly in this region.

The light adaptation curve itself illustrates how visual sensitivity changes as ambient light levels increase, and in region 3, where light adaptation is well-established, perceptions align with Weber's Law. Hence, the slope of 1 signifies that the perceived change in brightness is directly proportional to the actual change in light intensity.

The other laws mentioned describe different aspects of visual perception. Hering's Law pertains to color perception and the opposing pairs of colors. DeVries-Rose Law deals with the fractional change needed to perceive a difference in brightness under varying illumination levels. Rico's Law, while not as commonly referenced, typically pertains to visual response but does not specifically relate to the linear adaptation curve as Weber's Law does in this context.