A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. For comparison, the luminous efficiency of an incandescent bulb may only be 16 lumens per watt.
Linear fluorescent lamps illuminating a pedestrian tunnel
Top: two non-integrated compact fluorescent lamps. Bottom: two fluorescent tube lamps. Both types require a ballast in the light fixture. A matchstick, left, is shown for scale.
Typical F71T12 100 W G13 bi-pin lamp used in tanning beds. The (Hg) symbol indicates that this lamp contains mercury. In the US, this symbol is now required on all mercury-containing fluorescent lamps.
A "tombstone" style lamp-holder for T12 and T8 G13 bi-pin fluorescent lamps
Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionized gas, a plasma.
Germicidal lamps are simple low-pressure mercury vapor discharges in a fused quartz envelope.
Jules Verne's "Ruhmkorff lamp"
A compact fluorescent lamp
15 kW xenon short-arc lamp used in IMAX projectors
