Actually there’s three falloffs.
Each are added to the first, thus allowing turrets to increase range capacity, but as you get further out the lower your chances of hitting.
So a turret with 50km optimal and 50km falloff, within 50km and 100km (optimal + falloff) has a 50% chance of hitting, 100km to 150km (optimal + falloff + falloff) has a 6.25% chance, and from 150km to max range of 200km (optimal + falloff + falloff + falloff) 0.2% chance.
Only exception is Trig turrets as they have 0km falloff.
And only thing that effects these are ammo and tracking computer scripts these ranges adjust.
For example i have an Apoc with Beams that has a optimal range of 112km with radio and range scripts, and even with a signal booster running range script the beam will still hit targets in the first falloff range 50%, never getting target lock past the first falloff range.
While a Leshak with factional turret (longest optimal range of all trig turrets) using Meson ammo and 2x tracking computers running range scripts will hit a target just under 90km away. And that scares a lot of players when they see that happening, even those in the same fleet respect it after a few fleets, no longer view the Trigs as solely short to medium range ships.