A decade or two ago the only light bulbs available for the home and office were incandescent and some industrial style fluorescent tubes. Now the choice is much larger: bulbs are available in LEDs, halogens and energy saving.
Incandescent lights are available in 40, 60 and 100 Watt. Electric current passes through a very thin strip of tungsten metal filament; the light one sees is actually extreme heat, the light simply being a by-product. These globes are cheap but use comparatively more power than the other options. They are available as clear or pearl, round or candle shaped.
A halogen light bulb uses a tungsten filament as well, but where the gas in an incandescent bulb is argon, this gas is a halogen. It combines with the tungsten gas emitted by the filament and deposits the tungsten atoms back on the filament. As a result this type of bulb lasts much longer. It is available in 10, 20 and 25 watt bulbs; spot light bulbs of 35 watts and even 80 watt bulbs.
LED bulbs (Light Emitting Diode) emit light from a piece of solid matter and not from a vacuum or gas. The actions of the electrons cause them to emit light. With as little as 7.5 watts of supplied power, an LED emits up to up to the equivalent light of a 60 watt normal bulb. Most LED bulbs are not very bright and not really suitable for use as primary lighting in the home. They are available as 1.2, 2 or 4 watt and in warm white or daylight colour.
Energy saving bulbs, also called low energy, consist of glass tubes filled with mercury vapour. Through interaction between this gas and a coating on the inside of the glass, light is produced. These bulbs use only about 9 to 11 watts and are very energy efficient. Their initial higher cost is offset by the fact that they last a long time.