This document discusses light and the human visual system. It begins by defining light as electromagnetic energy and describes its properties like speed. It then explains how the eye works, including its parts like the iris, retina and photoreceptors. The document discusses color vision and theories around color perception. It covers topics such as color blindness, motion perception, and visual illusions. In summary, the document provides an overview of the science of light and how the eye allows humans to see color and perceive the visual world.