Illumination of emergency exits
9.1 Where an aircraft, which is equipped with an emergency lighting system in compliance with airworthiness directive Part 39-105 AD/General/4, is in flight and less than 1 000 feet above the terrain or on the ground with passengers on board, then either: (a) the emergency lighting system shall be switched on; or (b) the normal cabin lights shall be switched on and the emergency lighting system shall be armed.
Aeromuz, I have re-read your post, and you should do just fine at ground school. I misunderstood you first time around, It doesn't change my post however.
Fathom, I think you need to re-read what he said as well.
Having said that, although you are correct, it has nothing to do with why the lights are bright or dim?
They need to be in one of the "ON" positions, that's all is says. It's very dark inside a long aluminum tube, I cannot recall flying around with the lights "OF"