Karina, Bishops Stortford asked:
Why are streetlights orange?
The reason that most streetlights are orange is because they contain the chemical sodium. Some electricity is passed into the lightbulb and this gives energy to the sodium. Sodium, when it gets excited by the energy, gives out a lot of orange light. Making it a very cheap, and efficient way to illuminate a very large area.
I do not think that I like this answer very much. It is not really more complicated to produce white light than orange, and white lighting is mass produced for house lighting and building lighting anyway. Sodium lamps are no less expensive than various types of white lamps.
I believe the main reason they were originally adopted in a lot of places was simply because they put out more light for a given amount of power input - in other words, they were more efficient than the alternatives available at the time.
I would agree, it is easy enough to produce white light.
It must be, because a lot of bugs respond to specific wavelengths, and as your graphs show, the sodium lights only have a narrow output spectrum, so a lot less bugs will be affected.. Nizzle, Thu, 5th Apr 2012
And, since it's documented that bees can see into the UV it's fair to say that insects can see and respond to a range of wavelengths which rather brings that assertion "because a lot of bugs respond to specific wavelengths" into question. They can see a broader range of the em spectrum than we can. Bored chemist, Thu, 5th Apr 2012
However... whether or not the bugs can see different frequencies than humans,
The "yellow" of the light that we see in a bug light is not yellow light really in the same way that sodium light is -- it is essentially white light with all of the UV and visible violet filtered out: the mixture of ROYGB that remains is perceived by us as the "average" -- yellow. Yellow light like this can be obtained in two ways: a filament operating at "yellow heat", that is, somewhat cooler than the usual white hot filament, or by using an actual "sunscreen" type filter.
Could it be something to do with the fact white light is easily reflected in fog, whereas yellow light is not - like the fog lights in cars. Teresa, Tue, 10th Apr 2012