Why is mercury in compact fluorescent light bulbs (CFLs)?
Mercury is an essential part of a CFL, allowing it to be an efficient light source. There are electrodes at both ends of the fluorescent tube, and a gas containing argon and mercury vapor is inside the tube. A stream of electrons flows between the electrodes at both ends of the tube. The electrons interact with mercury vapor atoms floating inside the tube. The mercury atoms become excited, and when they return to an unexcited state, they release photons of light in the ultraviolet region of the spectrum. These ultraviolet photons collide with the phosphor coating the inside of the tube, and the phosphor glows, creating white light.
