CFL (Compact Fluorescent Lamp) converts electrical energy to radiant energy. They are energy efficient and use better technology as compared to conventional tube lights and bulbs. It has two components:
a) A glass tube filled with argon and mercury vapor & coated with a layer of fluorescent material.
b) An electronic ballast circuit
The ballast circuit takes a 220 V input from external power source and sends a current into the fluorescent tube as output. When power supply is given to the CFL, filament attached with the cathode heats up and emits electrons in the tube. This ionizes the argon and mercury vapor particles.
A 25 Watt CFL is shown in the above image.