How long does it take for 3% hydrogen peroxide to break down completely when exposed to light?

Hydrogen Peroxide. Hydrogen peroxide's chemical representation is h2o2. It has uses in industry in it's purest form but the product available to most of us over-the-counter is usually only 3% hydrogen peroxide and 97% water. It breaks down quickly when exposed to light so it generally comes in brown bottles that filter out the sun's rays. It is known for its antibacterial qualities.