What is Compact fluorescent lamp?
[[File:Compact_fluorescent_straight.jpg|thumb|250px|A three-U's type compact fluorescent lamp, popular with North American consumers since the mid-1990s.]] A '''compact fluorescent lamp''' ('''CFL'''), is a type of lamp (or light bulb) designed to fit into the same space and usually also the same [[wikt:socket|socket]] as an [[incandescent bulb]], but with the advantages of a [[fluorescent lamp]]. Many CFLs can directly replace an existing incandescent lamp. They were invented late in the 20th century and much used after the turn of the century (after 2000). The purchase price of a CFL is often much higher than an incandescent lamp of the same output, and the light from CFLs looks different to light from incandescent lamps.<ref>{{cite web|url=http://www.darksky.org/images/light_spec|title=Spectra of Different Light Sources|accessdate=2007-04-23|archiveurl = https://web.archive.org/web/20061209002431/http://www.darksky.org/images/light_spec |archivedate = December 9, 2006|url-status=dead}}</ref> CFLs have a longer rated life and use less [[energy]] than an incandescent lamp of the same brightness. A CFL can save over US$30 in electricity costs over the lamp’s lifetime compared to an incandescent lamp.<ref>{{Cite web |url=http://www.energystar.gov/index.cfm?c=cfls.pr_cfls |title=Energy Star CFL Introduction Page |access-date=2007-05-11 |archive-date=2008-09-16 |archive-url=https://www.webcitation.org/5at4Z0843?url=http://www.energystar.gov/index.cfm?c=cfls.pr_cfls |url-status=bot: unknown }}</ref> [[File:Elektronstarterp.jpg|thumb|250px|An electronic ballast]] As in other fluorescent lamps, electrified [[Mercury (element)|mercury]] vapor emits [[ultraviolet]] (UV) light. A [[phosphor]] converts it to visible light. The [[ballast]] prevents too much electricity from flowing through the tube. It is usually in the plastic base of the bulb. If the ballast is in the bulb, the bulb is called a self-ballasted lamp. Most are electronic ballasts. ==Lifespan== The average rated life of a CFL is 8 to 15 times longer th