Light Waves     The visible light wave spectrum encapsulates all of the colors visible to the human eye. It plays a large role in the art of drawing because it is quite literally what makes art a visual experience. http://science.hq.nasa.gov/kids/imagers/ems/visible.html     Drawing and sketching, whether in colored pencils or with charcoal and graphite, are a product of the visible light spectrum. The visible light spectrum allows the artist to use color and shading to give a two-dimensional image the illusion of being three-dimensional to the observer.   http://toparttips.blogspot.com/p/sketching-lesson-6.html Intro