In both cases the result is the same- The contrast between the object and the background approaches zero when the light coming along the line of sight from the object approaches the intensity of the light from the background at the horizon When the eye can no longer distinguish the difference, the contrast, between the object and the background the object can not be seen, and it is said to be beyond the limit of visibilityIn both cases, the result is the same— The contrast between the object and the background approaches zero when the light coming along the line of sight from the object approaches the intensity of the light from the background at the horizon. When the eye can no longer distinguish the difference, the contrast, between the object and the background, the object can not be seen, and it is said to be beyond the limit of visibility