SNELL - An Exploration of the Visual Refractive Status. When light passes from one medium to another with different properties, its direction and speed of propagation changes and the phenomenon of refraction occurs.Variations in color, direction and intensity are manifestations that allow us to verify that changes occur when light passes from one medium to another. We have created this set of images for the observation and experimentation of the phenomenon of refraction of light when it passes from a less dense medium (air) to a denser medium (water).