Least scattering capacity lets the color to be visible from long distances
Red color is used as danger light because of its less scattering capacity | Least scattering capacity lets the color to be visible from long distances
White light is the combination of seven colors. In these 7 colors, violet color has less wave length and red color has more wave length. In air, all seven colors of white light have same velocity. But when the colors are transformed to individual lights, different colors will have different velocities. In these seven colors, violet color has the least velocity and red color has the highest velocity among all. As blue color has more scattering capacity, it gets scattered more and so it cannot be visible clearly from long distances. But in case of red color with very less scattering capacity, it can be visible clearly from long distances.
So as red color has these three main important characteristics of 1) more wave length 2) more velocity 3) less scattering capacity, it is used as danger signal. So that it can be visible over a long distance. It was used as danger light due to this reason of good characteristics and not to create panic as it matches human blood which is red in color.