Light sources


Light can be produced from electricity in several ways and the most important are:

  • Incandescence Light and infrared energy are produced by raising the temperature of a substance (e.g. tungsten) until it is incandescent.
  • Electrical discharge Light is produced by electricity passing through a gas or vapour, agitating or exciting the atoms of the filling to produce light, UV energy and infrared energy.
  • Fluorescence and phosphorescence The process by which UV energy is converted into visible light by phosphors.


Lumens per watt

100W household lamp


3200 K tungsten halogen lamp


HF fluorescent lamp


HID lamp 6000 K


Table 5.1 Output as a percentage of input power

3200 K Incandescent lamp

Losses ...

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