How does a CFL or other fluorescent light bulb work?
A CFL or other fluorescent light bulb is made up of a phosphor-coated glass tube that contains some mercury vapor. When the electric current is switched on, the mercury vapor is energized, causing it to send out ultraviolet (UV) energy. The phosphor coating absorbs the UV energy, which causes the phosphor to fluoresce and send out visible light. Without the mercury vapor to produce UV energy, there would be no light.
