No matter where the light comes from, its intensity
will always be greater at the narrow end of the cone where the intersecting area
is smaller.
The intensity of light falls off as the square
of the distance from the NARROW END OF THE CONE, not from the source of
light. This is due to the fact that the intersecting area is the denominator
in the equation for the intensity of light. The drop in intensity tracks the
increase of this area, which increases as the square of the distance away from
the narrow end of the cone. The intensity of a LASER
beam remains constant over vast distances because the light in a LASER beam
does not spread out into a light cone, ie the intersecting or cross-sectional
area of the Laser beam is the same at both ends.