First Question: I think I have the question worded correctly. How many seconds would it take for the luminosity of an area to double if the amount of input light was unchanged, but the output light was forced to remain in the same place? Second Question: There are 2 rooms. One room has lights, the room is well lit. The 2nd room has no lights, and is pitch black. Neither rooms have windows. There is a door between the two rooms, which is open. I am standing in the pitch black room, looking through the door, into the well lit room. Objects can only be seen when light reflects off of them, other wise they are pitch black. I can see clearly what's in the well lit room. Light must be reflecting off the objects towards my direction for me to see them. How come if light is being reflected in my direction, I am not visable?