A Sylvania Roadster high pressure sodium vapor street lamp from Australia.
From the en.wikipedia.org
A common application of the compounds of sodium is the sodium vapor lamp, which emit very efficient light.
From the en.wikipedia.org
For instance, a sodium flame can emit yellow light as well as absorb the yellow light from a sodium vapor lamp.
From the en.wikipedia.org
In a sodium-vapor lamp for example, sodium atoms are excited to the 3p level by an electrical discharge, and return to the ground state by emitting yellow light of wavelength 589 nm.