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.
Sodium Vapor Lamp Media
A high-pressure sodium street light in Toronto
A high-pressure sodium-vapor lamp
A low-pressure sodium lamp running at full brightness
An unlit 35 W LPS/SOX lamp
Warm-up phases of a LPS lamp. The faint pink light of the Penning mixture is gradually replaced by the bright monochromatic orange light of the metallic sodium vapor.
A running 35 W LPS/SOX lamp
Spectrum of a low-pressure sodium lamp. The intense yellow band is the atomic sodium D-line emission, comprising about 90% of the visible light emission for this lamp type.
Two Honda Fits under low-pressure sodium lamps. Both appear black, even though the car on the left is bright red, while the car on the right is actually black.
High-pressure sodium lamp in operation
Spectrum of high-pressure sodium lamp. The yellow-red band on the left is the atomic sodium D-line emission; the turquoise line is a sodium line that is otherwise quite weak in a low pressure discharge, but becomes intense in a high-pressure discharge. Most of the other green, blue, and violet lines arise from mercury.
