Lamp theory

Artificial light, meaning something other than  sunlight, may 
beproduced either  chemically, mechanically, or electrically. 

Chemical light is used for very special applications, such as 
the emergency wands that you see in sporting goods stores; 
mechanical (flame –gas lamps)  is primarily used to create
atmosphere. 
By far, the greatest producer of usable artificial light is electricity. 
The electrically driven light source is what we will examine here.
The two most important methods by which we can produce light
from electricity are incandescence and photoluminescence. 
These are big words used to describe the processes by which 
the lamps that we use every day produce light. Let’s see how 
each of these processes works.