[Corvettaholic]

I think messing with colors falls under this category  

I remember way back when in high school chemistry we had these (forgot name of device) that showed us all the colors in the spectrum a particular element had. Like neon was bright orange and stuff like that. Most elements have more than one color. I think the word I'm looking for is spectronomy or something like that? Anyway, what I'm wondering is how do you get a specific element to give off a specific color so I can see it? Fill a tube with the (gaseous) element and apply high voltage? Does the amount of voltage change the color?

[Mitch]

Your setup is accurate. No, voltage won't change the color just the intensity.

[Corvettaholic]

Voltage = Intensity, got it. Is it possible to apply too much voltage? What happens then? When the gas starts letting photons go, its still a gas, right? I don't want a plasma to form, because I was also wondering if I can contain the gas in a thick transparent plastic tube. That would keep fabrication costs way down, due to the fact that I don't know how to blow glass.

Now to get the different colors out of a particular gas, would changing the frequency help, or do I have to use DC? I can get my paws on a transformer that'll put out 30kHz, or I could use plain ol 60hz wall outlet voltage.

[jdurg]

I don't think you can change the color of the gas without changing the gas.  The color emitted from the gas is characteristic of the electron configuration of the gas.  You simply can't change that.

[Corvettaholic]

So a gas will only give out one color, too bad. But whats the deal with all the different colors I see associated with one particular element?

It may be accepted science that the gas will only give off one color, but I think I'll have to test that for own education. I think a 10 stage cockcroft-walton impulse genereator will do the trick, 1 megavolt!

[movies]

A gas could emit in different parts of the visible spectrum though, so there could be multiple colors, right?  You can only get one color per transition though.

[Corvettaholic]

So if a gas is emitting in different parts of the visible spectrum at the same time, why is it that we can only see one color at a time? Lets take a look at neon signs, do they use exclusively neon? If a gas can only give off one color, they can't all be neon because there are different colors in the signs... or is colored glass? So lets say you have a tube of nitrogen and it gives color x, but you want to see color y. How do you get color y to show up as opposed to color x?

[movies]

In "neon" signs I think they use different gases to get the different colors.

[Corvettaholic]

You know, I think you're right. I remember reading some article on neon signs. If you look at one up close, you'll notice small little sections with no color that are in the tube. I imagine that part seperates one tube into two, which allows containment of 2 different gasses. I'd also wager a guess that the high voltage that powers the tube, somehow gets passed along to the next gas tube. How? Dunno. Maybe inductance or a small conductor I can't see.

If I can figure out how to get more than one color out of a specific gas, I'll be sure to let you all know!

[jdurg]

Correct.  Sadly, the term 'Neon Sign' has become used to describe ANY gas discharge tube used for signage.  Those tubes can contain anything from sodium vapor, mercury vapor, argon, nitrogen, xenon, neon, etc. etc.  Any one particular gas will only emit one specific color unless different filters are used.  Let's take Neon, for example.  Put low pressure neon gas in a discharge tube and apply some voltage, and you'll see the distinct bright-red color of Neon.  However, Neon's emission spectrum also includes wavelengths of other colors.  So if you could filter off the red color, you may be able to see the other ones.  So if you had a tube which was lined with a compound that absorbed red light but allowed other colors to go through, that 'Neon' gas would look either bluish or yellow.  So a gas does produce more than one color, however the color we see is due to a greater intensity of said color.  (Like in neon, the reds and oragnes are a higher intensity and more prevalent than the blues and yellows, so to us Neon gas has a red-orange color).


So the only way to get multiple colors out of a single gas is to use filters or special coatings on the tubes.

[Corvettaholic]

Now its perfectly clear, here's a scooby snack jdurg! So instead of trying to mess with the gas, I need to design an adjustable filter. How do I filter out something that has a wavelength in nanometers anyway?

[jdurg]

Now its perfectly clear, here's a scooby snack jdurg! So instead of trying to mess with the gas, I need to design an adjustable filter. How do I filter out something that has a wavelength in nanometers anyway?

Heh.  Beats me.  

[Donaldson Tan]

adjustable filters.. i think snell's law would come in handy. different light would refract differently because of different wavelengths. An adjustable filter would contain a substance with adjustable optical density, so that light whose wavelength fall within a certain range would be refracted and exit at a particular aperture..

perhaps u can build your filter by using placing panes of glass, each with a different refraction index. their configuration would decide which wavelength range you are selecting for.

[Corvettaholic]

What would be fairly snazzy is to have only one lense, with adjustable optical properties as opposed to having several filters where I have to manually (or robotically) move. Isn't there special types of glass that change their opacity based on an input voltage? I think bill gates has crap like that in his all glass house...