This study investigates high school students' knowledge of natural phenomena related to the concept of light flux (seasons, illumination) after they had learned optics. It is suggested that such knowledge be represented as a hierarchical structure of schemes and facets. The two naive schemes that prevail in students' knowledge fail to represent the formal scientific model for the subject. The problem of the student's  failure to account for the phenomena is analyzed from several aspects. It is shown that current curricula lack the required conceptual tools: light flux, illuminance, and the law of illumination, all of which have gradually disappeared from textbooks in recent years. Light rays provide the sole framework in the current teaching of geometrical optics. Historically, the paradigm of light rays has been succeeded by that of light flux. Didactic, cognitive, and ontological perspectives are discussed in relation to specific implementations in science curricula and instruction. The changes suggested might have a positive impact on prevention of many currently prevailing misconceptions in optics.