Definition
An electric discharge lamp that produces light by passing an electrical current through ionized sodium vapor inside a sealed glass tube. The result is a distinctive yellow-orange light that is highly efficient and penetrates fog and haze better than white light.
Plain English
A type of light bulb that glows yellow-orange because it makes electricity flow through sodium gas. It uses very little power for the amount of light it produces and shows up well in bad weather.
Context Anchor
Pilots may notice sodium-vapor lamps around ramps, hangars, parking areas, roads near an airport, or other outdoor airport lighting areas.
Derivation
Sodium is the metallic element that produces the yellow glow when vaporized and excited by electricity. Vapor refers to the gaseous state of the sodium inside the lamp. Together, the name describes exactly how the lamp works: light from sodium in vapor form.
Why Pilots Care
These lamps penetrate fog and haze effectively, giving pilots clear visual cues for runway alignment during night and low-visibility operations.
Intuition Check
Do not assume this is just a normal light bulb with yellow glass. In a sodium-vapor lamp, the yellow color comes from glowing sodium vapor inside the lamp.
Example Sentence 1
The ramp was lit by sodium-vapor lamps, giving the parked aircraft a warm orange tint.
Example Sentence 2
During the night preflight, the ground crew checked that all sodium-vapor lamps on the taxiway were illuminated.