Sodium vapor lamp

A sodium vapor lamp is a kind of gas discharge lamp. Streetlights are a major use. There are two types; the high pressure lamp and the low pressure lamp. The older low pressure one gives yellow light. It is still used where the ability to show different colors is not very important. The newer high pressure sodium vapor light emits a broader spectrum, often appearing orange but letting people see different colors. 
These lights contain sodium metal in them. They operate by a spark through a tube that contains the sodium. The sodium emits a yellow color, which produces the light. Because the lamp contains highly flammable sodium as well as toxic mercury, it should not be placed in the trash and must be disposed of properly at the end of its life.