Flash Distances Diagram

Direct flash follows black line.
Background flash follows blue line.
Bounced fill flash follows red line.

If the aperature is adjusted to keep exposure of the subject the same, the exposure of the background and of the fill will change based on the distance (length of the line). The ratio between the lengths determines the relative exposures.

With a close flash (bottom), background light goes further than the direct light to the subject. However, the fill light goes much, much further.

With a far flash (middle), background and fill light goes further, but not as much further as in the close flash.