Fluorescent Tubes
These are commonly available as circular or long tubes in various wattages. A ballast and starter are normally housed inside the light fitting. Alternatively, an electronic controller can be used to replace these. The most commonly available tubes produce a 'cool white' light, although tubes are available which produce a 'warm' light.

Advantages

• Energy efficient.
• New versions operate at a much higher frequency practically eliminating flicker.
• New versions are about 25% more efficient than older versions.
• Very long lasting.

Disadvantages

• Lights operated with the standard ballast and starter arrangement tend to flicker, especially as the tube ages.
• They are relatively expensive.
• Not dimmable
• Physically larger than most incandescent lamps
• Requires a type specific lamp fitting.