We are required to solve the riddle <em>"when it wakes up it becomes brighter when it falls asleep it becomes dark"</em>
The answer to the riddle <em>"when it wakes up it becomes brighter when it falls asleep it becomes dark"</em> is match stick"
A match stick is a device made of wood or paper, at the tip coated with chemicals that ignite with the friction of being dragged (struck) against a rough dry surface. It could be used to light cigarette.
Riddles are verbal puzzle, mystery, or other problem of an intellectual nature.
Therefore, the answer to the riddle is "match stick".
