fluorescent light is another light source which happens to be my favorite
light source as a bulb collector. Today fluorescent light is
far more common than the incandescent
How it Works: The basic principle of operation of a fluorescent lamp
is simple. You have a
 |
| fluorescent light |
glass tube, on each end are electrodes called Cathodes,
and in the case of a hot cathode type lamp they are a little filament, that is
why you have two pins on each end because each pin goes to one end of the
filament, and these filaments inside are electrodes that send current through
the gas in the lamp the gas in the lamp is argon, and there is a little bit of
mercury in the tube, just a tiny amount just a pinhead amount of mercury.
And how it works is when the current is switched on these cathodes
head up and they are coated with a special material that gives off electrons,
it works on the same principle as the vacuum tube and it's called thermionic
emission, when it heats up it gives off electrons, and that is good because when
they heat up they give off electrons then a high voltage pulse is sent through
the lamp from the starter and that pushes those electrons through the lamp from
one end to the other and it starts and arc through the lamp through the gas
that is in the lamp which is argon, and this argon arc makes enough heat to
vaporize the mercury that is in the tube and that goes into the arc stream and
produces ultraviolet radiation ultraviolet light, and this UV light hits a
powder on the inside of the tube that is why they are white it's called a
phosphor, it's a material that glows when ultraviolet radiation strikes it.
When it hits the phosphor, it makes it glow. and that is what
produces light.
Now what I'm going to do is start up a nice Sears fluorescent lamp
that was made by Westinghouse and branded as Sears, they are not common today that
starts in a preheat fixture with a "Starter", and you'll be able to
see the preheating of the lamp when I start it
Beautiful start, you see it blinked a couple of times because the
lamp didn't catch on the first try
So the starter just re-glowed, heated, closed the contacts and tried
again and the starter will keep trying until it restarts the lamp there is a
little delay, there is the cathode heat, there is the start, beautiful start
The starter is really good in this fixture, this [preheat type] is
the design that came out in 1939 and it is still with us today and it is
unbeaten in reliability
The reason why they have different colors: warm white, cool white,
even solid colors similar to pink, blue and green
The reason why they create different colors is because there are
different blends of the chemicals used in the phosphors, like for example if
you took the phosphors of the blue lamp and mixed it with phosphors from a pink
lamp you could get a white lamp and in fact this cool white lamp I have in my
hand has a specific blend of the blue phosphors and the pink phosphors, makes
white by using a certain balance.
So the blue and the reds balance together and produce a white light.
Of course there are other colors emitted too blue and red are the predominant
colors, and the simplicity of the lamp is the advantage another advantage that
it doesn't get hot, the ends get a little hot to the touch because of the
filaments but not hot enough to burn you, the center runs lukewarm because the
current flowing through the gas produces mostly UV light and it's at low
pressure, so it doesn't produce a lot of heat which is an advantage because
Fluorescent lamps can produce a lot of light on very little energy.
For general lighting, inside of buildings for white fluorescent light can not
be beat in efficiency, it doesn't matter if you have an old fixture from the
1940s that uses starters and has ancient electrical gear inside of it or the
most modern electronic ballasts the efficiency of the lamps hasn't changed much
over the years, the disadvantages are few maybe sometimes contact issues, they
don't want to start sometimes things like that. If you turn the lamp on and off
frequently you can shorten its life
Color quality of the light isn't as good as incandescent, that is
another disadvantage, but their advantages outweigh their disadvantages.