Hi, I just had a chance to play with a spectrometer. It's just a little
cheap one that belongs to my sister-in-law who teaches 4th grade.
Naturally, I took a look at my plant lights. I remember being told that
all you really need is cool white fluorescents. Of course, being an
orchid grower, good enough is never good enough. Some people add warm
whites. I don't, but I do add in some Gro-lux wide spectrum tubes. They
look very pink so obviously they add in some of the red spectrum missing
in cool whites ... or do they?
I'm looking through the spectrometer at a cool white and there is a bold
bright line in the blue range at about 435 nm, a bright green line at
about 535, and a good red line at just over 600.
Then I look at the wide spectrum tube, and it looks just the same except
there is no red line. Now I'm wondering how the tubes can look pink but
have less red that a cool white?
I know... there are places on the internet that show a very accurate
spectrum for many kinds of light. Maybe that would answer my question if
I looked long enough.
Of course, I also took a look at my metal halide lights and the HP
Sodium light. My comment on the MH is that there certainly is a lot
going on in the green part of the spectrum where the light isn't very
useful. I couldn't really isolate the HPS bulb because it shares a
fixture with another MH bulb. I could unplug the MH but there is a
window right next to it with sun streaming in at the moment. After
sunset, it might be worth checking the HPS alone.

Steve

Steve, with flourescents the line spectra are from the gas within the tube. The
first one sounda like neon; the second one should be as well, I would have
thought, but I've no idea where the red line went. The fluorescent coating on
the inside of the tube is what is intended to provide the illumination - it
fluoresces when electrons & ions from the gas (neon) discharge within the tube
strike it. The fluorescent coating should provide a continuous spectrum,
weighted towards that end of the spectrum it was designed to provide - ie the
blue end for a "cool" tube" & the yellow/red end for a "warm" tube. This
continuous spectrum is what you should be concentrating on - not the gas lines.

Mwtal halide lamps are still hot wire lamps - ie a continuous spectrum. But
they get much hotter than a normal tungsten lamp - more efficient illumination
that way. Anyway, a hot wire will still give a continuous spectrum. The lines
you see would probably relate to the halogen gases which fill the tube.

Your sodium lamps should show quite a colourful line spectrum, with two
prominent yellow Na D lines that provide the characteristic amber sodium colour.

On Sun, 22 Jan 2006 15:19:12 -0500, Steve <tlswilso [at] aol.com> wrote:

>Hi, I just had a chance to play with a spectrometer. It's just a little
>cheap one that belongs to my sister-in-law who teaches 4th grade.
>Naturally, I took a look at my plant lights. I remember being told that
>all you really need is cool white fluorescents. Of course, being an
>orchid grower, good enough is never good enough. Some people add warm
>whites. I don't, but I do add in some Gro-lux wide spectrum tubes. They
>look very pink so obviously they add in some of the red spectrum missing
>in cool whites ... or do they?
>I'm looking through the spectrometer at a cool white and there is a bold
>bright line in the blue range at about 435 nm, a bright green line at
>about 535, and a good red line at just over 600.
>Then I look at the wide spectrum tube, and it looks just the same except
>there is no red line. Now I'm wondering how the tubes can look pink but
>have less red that a cool white?
>I know... there are places on the internet that show a very accurate
>spectrum for many kinds of light. Maybe that would answer my question if
>I looked long enough.
>Of course, I also took a look at my metal halide lights and the HP
>Sodium light. My comment on the MH is that there certainly is a lot
>going on in the green part of the spectrum where the light isn't very
>useful. I couldn't really isolate the HPS bulb because it shares a
>fixture with another MH bulb. I could unplug the MH but there is a
>window right next to it with sun streaming in at the moment. After
>sunset, it might be worth checking the HPS alone.
>
>Steve
Dave Gillingham
------------------------------------------------------------ ------------------
To email me remove the .private from my email address.

I don't know that I agree with that, Dave.

It is my understanding that the energized gas in the tube (typically a small
amount of mercury in an inert gas like argon) emits photon energy in the
ultraviolet part of the spectrum as the ions "collapse" to a lower energy
state. It is the UV that excites the phosphors, and they are solely
responsible for the visible light emitted. That phosphor composition is
varied to give different spectral " blends."

Neon would be a terrible gas to use in a fluorescent light, as the red color
of neon emission shows it to be insufficiently energetic for causing
anything to fluoresce.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Artwork, Books and Lots of Free Info!


"Dave Gillingham" <dewg [at] private.optusnet.com.au> wrote in message
news:2i29t1hp4qead4em0eg0m1s4kfnqtppmdk [at] 4ax.com...
> Steve, with flourescents the line spectra are from the gas within the
> tube. The
> first one sounda like neon; the second one should be as well, I would have
> thought, but I've no idea where the red line went. The fluorescent
> coating on
> the inside of the tube is what is intended to provide the illumination -
> it
> fluoresces when electrons & ions from the gas (neon) discharge within the
> tube
> strike it. The fluorescent coating should provide a continuous spectrum,
> weighted towards that end of the spectrum it was designed to provide - ie
> the
> blue end for a "cool" tube" & the yellow/red end for a "warm" tube. This
> continuous spectrum is what you should be concentrating on - not the gas
> lines.
>
> Mwtal halide lamps are still hot wire lamps - ie a continuous spectrum.
> But
> they get much hotter than a normal tungsten lamp - more efficient
> illumination
> that way. Anyway, a hot wire will still give a continuous spectrum. The
> lines
> you see would probably relate to the halogen gases which fill the tube.
>
> Your sodium lamps should show quite a colourful line spectrum, with two
> prominent yellow Na D lines that provide the characteristic amber sodium
> colour.
>
> On Sun, 22 Jan 2006 15:19:12 -0500, Steve <tlswilso [at] aol.com> wrote:
>
>>Hi, I just had a chance to play with a spectrometer. It's just a little
>>cheap one that belongs to my sister-in-law who teaches 4th grade.
>>Naturally, I took a look at my plant lights. I remember being told that
>>all you really need is cool white fluorescents. Of course, being an
>>orchid grower, good enough is never good enough. Some people add warm
>>whites. I don't, but I do add in some Gro-lux wide spectrum tubes. They
>>look very pink so obviously they add in some of the red spectrum missing
>>in cool whites ... or do they?
>>I'm looking through the spectrometer at a cool white and there is a bold
>>bright line in the blue range at about 435 nm, a bright green line at
>>about 535, and a good red line at just over 600.
>>Then I look at the wide spectrum tube, and it looks just the same except
>>there is no red line. Now I'm wondering how the tubes can look pink but
>>have less red that a cool white?
>>I know... there are places on the internet that show a very accurate
>>spectrum for many kinds of light. Maybe that would answer my question if
>>I looked long enough.
>>Of course, I also took a look at my metal halide lights and the HP
>>Sodium light. My comment on the MH is that there certainly is a lot
>>going on in the green part of the spectrum where the light isn't very
>>useful. I couldn't really isolate the HPS bulb because it shares a
>>fixture with another MH bulb. I could unplug the MH but there is a
>>window right next to it with sun streaming in at the moment. After
>>sunset, it might be worth checking the HPS alone.
>>
>>Steve
> Dave Gillingham
> ------------------------------------------------------------ ------------------
> To email me remove the .private from my email address.

Dave Gillingham wrote:
> Steve, with flourescents the line spectra are from the gas within the tube. The
> first one sounda like neon....


No. Fluorescents use argon, not neon.


J. Del Col

Original post:
==========
>No. Fluorescents use argon, not neon.
==========

Fluorescent lights use a variety of inert gases in addition to the
mercury and fluorescent phosphors they contain. Argon is common, but
neon may also be used, sometimes in an Ar/Ne mixture.

James Aldridge, Ph.D.
Fort Worth Country Day School
Departments of Science & Computer Science
jaldridge [at] fwcds.org
============================================
James Aldridge - Fort Worth, Texas, USA
www.JamesAldridge.com - jaldridge [at] uwmail.com

Oops! Meet you half way, Ray. You're dead right about the excited vapour atoms
emitting uv which causes the phosphor to fluoresce. It's the electrons of the
discharge which boot those atoms up to the excited states from which they relax,
emitting uv. But still, the lines to which Steve was referring are from the gas
discharge, which is incidental to the illumination function of the tube. That
comes from the continuous spectrum emitted by the phosphor.

On Mon, 23 Jan 2006 18:25:24 -0500, "Ray" <raybark [at] firstrays.com> wrote:

>I don't know that I agree with that, Dave.
>
>It is my understanding that the energized gas in the tube (typically a small
>amount of mercury in an inert gas like argon) emits photon energy in the
>ultraviolet part of the spectrum as the ions "collapse" to a lower energy
>state. It is the UV that excites the phosphors, and they are solely
>responsible for the visible light emitted. That phosphor composition is
>varied to give different spectral " blends."
>
>Neon would be a terrible gas to use in a fluorescent light, as the red color
>of neon emission shows it to be insufficiently energetic for causing
>anything to fluoresce.
Dave Gillingham
------------------------------------------------------------ ------------------
To email me remove the .private from my email address.

James Aldridge wrote:
> Original post:
> ==========
> >No. Fluorescents use argon, not neon.
> ==========
>
> Fluorescent lights use a variety of inert gases in addition to the
> mercury and fluorescent phosphors they contain. Argon is common, but
> neon may also be used, sometimes in an Ar/Ne mixture.


Argon isn't just "common" it is the overwhelming choice. The
Ar/Nemixture is rarely encountered. Some special purpose tubes use
krypton, but they are even rarer than the tubes with neon.


J. Del Col

Thanks for the discussion, guys. Those few color lines were so bold and
bright compared to everything else, I figured those lines were most of
the light being emitted. Maybe not.
I don't think my sister in law took the spectrometer back yet. If it's
still here this weekend, I might look at it again.

Steve


Dave Gillingham wrote:
> Oops! Meet you half way, Ray. You're dead right about the excited vapour atoms
> emitting uv which causes the phosphor to fluoresce. It's the electrons of the
> discharge which boot those atoms up to the excited states from which they relax,
> emitting uv. But still, the lines to which Steve was referring are from the gas
> discharge, which is incidental to the illumination function of the tube. That
> comes from the continuous spectrum emitted by the phosphor.
>
> On Mon, 23 Jan 2006 18:25:24 -0500, "Ray" <raybark [at] firstrays.com> wrote:
>
>
>>I don't know that I agree with that, Dave.
>>
>>It is my understanding that the energized gas in the tube (typically a small
>>amount of mercury in an inert gas like argon) emits photon energy in the
>>ultraviolet part of the spectrum as the ions "collapse" to a lower energy
>>state. It is the UV that excites the phosphors, and they are solely
>>responsible for the visible light emitted. That phosphor composition is
>>varied to give different spectral " blends."
>>
>>Neon would be a terrible gas to use in a fluorescent light, as the red color
>>of neon emission shows it to be insufficiently energetic for causing
>>anything to fluoresce.
>
> Dave Gillingham
> ------------------------------------------------------------ ------------------
> To email me remove the .private from my email address.