Electrical Power Systems Technology

Lighting Systems 329

When dealing with light, there are several characteristic terms that

you should understand. The unit of luminous intensity is a standard light

source called a candela or candlepower. The intensity of light is expressed in

one of these units. The amount of light falling on a unit surface, all points

of which are a unit distance from a uniform light source of one candela, is

one lumen. The illumination of a surface is the number of lumens falling

Figure 13-1. The electromagnetic spectrum