where are all the photons before you turn on the light?

Factual Questions
21

>> This is the approximate reason why incandescent bulbs can have dimmer switches (just cool the filament by running less electricity and you get less light) but in general flourescents cannot (its either on or off - the quantum jumping thing again.)

Douglips, I do not believe this is correct. The reason you cannot use a normal dimmer on a fluorescent lamp is that it has an inductive ballast to limit the current which is therefore not in sync with the voltage etc. But if you could build a variable ballast you could regulate the current and the luminosity. Some newer fuorescents with electronic “ballast” can indeed be dimmed. You can try this: Take any regular flourescent and, once it is on, insert a resistor in series that will decrease the current and you will see the luminosity decrease. I guess you could also switch ballasts…

22

I believe you are right, sailor. Dimming a flourescent bulb is more complex, because, well, running a flourescent bulb is more complex. With an incandescent, it’s easy - run current through the bulb and you get light - run less and you get less light. In the flourescent case you have to deal with the ballast etc.

And, now that you mention it I’ve seen flourescent lights on dimmers before and wondered to myself “How the heck does that work”, so I don’t know why I said something so silly as “you can’t dim flourescents”.