GillBates
Newly Enlightened
1.2km+ led spotlight does something like this exist? If so what would be a good light to purchase?
More seriously, is 0.25 lux
Which works out at 300000+ lux at 1 metre for 0.25 lux @ 1.2km. Inverse Square Law.
E1=(D1/D2)^2 * E2
Where E1 is output at D1 and E2 is output at D2.
That depends on the light source. A laser won't obey that law, nor will a light that uses a parabolic reflector (at least not if you measure it from the distance of the light).
It roughly applies if you are far away enough (which might mean several hundreds of meters, though).
But what issue do you have in mind for reflectors? (except, as always, if distance is too short). I never noticed any until now.