Simple grammar question. Thanks!
A typical glass mirror has a substance painted on one side, you can use black paint for instance.
Open the thing and take out the battery. If it's wired into your home, then yes, you are screwed and you'll need to call in an electrician? It sounds as if the battery needs replacing to be honest.
a mirror has something reflective on the back side. Good ones have a layer of silver or aluminum deposited on the glass, after it has been polished. Then the metal is covered with paint or other protective materials. The glass is just to protect the thin layer of aluminum or silver from damage or corrosion. .
