Re: why does placing a candle in front of a mirror not increase the total light

  If you place a candle in front of a wall, then roughly half the
candle's light shines into the room, and the other half shines into
the wall.  If the wall is a dark color, most of the light which 
hits it is absorbed by the surface.  If it's a light color, then
a reasonable fraction of the light bounces off the surface and
returns to the room.

  If you place a mirror on the wall behind the candle, you are
simply increasing the fraction of the light which bounces off
the wall.  Yes, the room will probably be lit a bit more brightly
than before, since fewer light rays will be absorbed by the 
mirror than by the wall.

  There's no conflict with the law of conservation of energy.
The candle produces the same amount of light in both cases;
you are simply re-directing more of it back into the main portion
of the room with the mirror.