::::::As it stands, the present article is about light as physical phenomenon: a category of electromagnetic radiation (others include X-ray, Gamma ray, Radio wave, Infrared, Microwave and Ultraviolet because each is a significant topic in itself beyond the broader Electromagnetic radiation article).  The main mention of vision in the present article is to define the "visible" wavelengths, which hardly makes it an article covering the related perceptual/psychophysical/physiological phenonmena, which already have (and deserve) their own articles such as Visual perception and Visual system, and even Photometry and Color which are also defined with reference to human observers.  (Perhaps the present article should refer to those for further information.) The editors of Sound, in contrast, decided to make that article about both the physical phenomenon and the perceptual phenomenon: it says so explicitly at the beginning of that article.  Because WP is not a dictionary, it isn't necessary that the article called Light cover all meanings or topics described by this word.  The present Light article is in the Category:Light category, which in turn is in Category:Optics, Category:Electromagnetic spectrum, Category:Electromagnetic radiation, Category:Waves, and Category:Electrodynamics, none of which are psychological or biological.  If you really think there should be a blanket article beyond Visual perception and Visual system that connects these in some additional way to light (and hopefully you might contribute to its creation), it could be called (just for example) Light (vision) (and could be added to Light_(disambiguation)), but I don't think this topic should be fully merged into the present article which stands well on its own.