Exploring the Difference Between Incandescent and Mercury-Vapor Lights

[stickythighs]

By definition, are all mercury-vapor lights NOT incandescent lights?

In practice, are mercury vapor lights ever incandescent lights?


Are most street lights in the United States incandescent lights or mercury-vapor lights or sodium vapor lights or some other type of lights?

 

[mgb_phys]

Incandescent lights are ussually defined as those that glow because of the blackbody emission from a hot filament (incandescent=heat).
Fluorescent lamps (including Hg and Na) emit light in discrete lines from electron transitions. Low pressure sodium uses only a single line (actually a close together pair) so you get only a single colour (orange) but it is efficent since almost all of the energy goes into this line. Mercury gives a much whiter ligth because it has so many lines and the pressure of the vapor broadens them so they almost overlap - giving a nearly continuous spectra.
The other class of lights would be LEDs but they aren't used in street lighting - yet.

 

[stickythighs]

So by definition Mercury-vapor lights are not incandescent lights?

 

[russ_watters]

Correct.