Dear 100 Hour Board,
Lets say you are in a bright room with no windows or anything, and it is dark outside. Then you open a door, does it get any darker inside, even by a fraction? I would think that since some of the light is going out side that maybe the light would be less bright/concentrated.
- Lucy Pevensie
Absolutely. The light that would have reflected off the door and back into the room is now leaving without ever having a chance to hit your eyes.
An easy way to think of this is to imagine that the door is slowly growing along the walls. Obviously, if the door grows to the point that you only have one wall remaining, it's going to be darker in the "room" than when you were surrounded by walls. The question then becomes: Is there some magical point at which the room starts to become darker? If so, what is special about that point? There's no reason why a door of 25 square feet would darken the room while a door of 5 square feet wouldn't; the door certainly isn't suddenly too small for the light to pass through.
So since there's no point at which the light would stop escaping, we can only conclude that so long as there is a hole, some light is escaping from the room.