What coffeking said. In terms of ‘seeing’ light is focussed by the lens onto a point on your retina called the fovea which has cells (rods and cones) sensitive to light. Some are specialised for colour vision (cones) and others for low light conditions (rods). They detect the light, send an electrical signal via the optic nerve to the brain, which deciphers the messages and interprets it as an image.
As you move away from the source it is reduced in intensity by a cube of the distance by the way, i.e. double distance from source intensity falls by 8 times