The full form of CFL is Compact fluorescent lamps. CFL is an energy-saving bulb that consumes much less energy than the conventional incandescent lamps. It is made of a glass tube, along with two electrodes. The glass tube contains a mixture of argon gas & mercury vapour and is filled with phosphorus on the inner surface.

Working principle of CFL

CFL has various illumination generating pathways than that of the incandescent lamps. An electric current in a bright light travels via a wire filament. It heats the thread to create a light, as well as the filament glows—the current in CFL transfers via the tube that contains the blend of argon gas & mercury vapour. The current activates the mercury vapour that generates UV light.

Source: Lucent