Fluorescent lamp questions


Senior Team Emeritus
Premium Member
Fluorescent lamps run fairly cool to the touch. They don’t really emit any real heat. Yet it’s an arc source lamp and has an arc of electricity running between electrodes. A normal arc source lamp runs at temperatures in excess of that of a halogen lamp. So what’s the story here?

Why is it that a fluorescent lamp can get away with for the most part plastic lamp bases, much less can go up to 96" long and have an arc, yet other types of arc source lamps have fairly small arc lengths. In arc length, how is it that you can have a say 11" arc length on a Xenon strobe lamp yet most have fairly small arc lengths?

Bonus points is at the end of the lifespan of a 12 or 20 year ballast to a fluorescent. How does it now emit heat in melting down stuff like tube guards or lamp bases?

Back to Radium Brand AR-111 lamps for me...


Well-Known Member
Well I haven't formulated my theory yet, though I am willing to share my existing knowledge to maybe help piggy-back someone. I know that when an atom gains energy its electrons go into a higher energy level. When the atom is in this higher energy level it does not give off light, indeed it is when the electrons drop down into a lower energy level that light is emitted. That's about it.


One of the reasons that fluorescent lamps run cooler is that the arc does not run the length of the tube. There are two arcs in a fluorescent lamp one at each end, so the arc is only between the two posts at the end of the lamp. Also the arc does not create the light in the lamp. How a fluorescent lamp creates light is that the arc excites the argon and mercury gas sealed in the tube. The excited argon glows and white light is created due to the interaction between the phosphoric coating on the outside of the lamp and the energy from the excited argon.

To go for the bonus points, I am pretty sure this is right but I could be wrong... A ballast that is current at 12 or 20 years is most likely an older magnetic style ballast, which has less control at the end of its lifespan then the newer electronic ballasts have.

Steven B.


Active Member
Pretty much right about the interaction between the mercury/argon and the phosphorous, but remember, the mercury/argon is glowing at frequencies we can't see and the phosphorous is transferring that into visable light. It's a big reason why flourescent lights are so much more effecient, they aren't really creating visable light.

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